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vb.net : Can I make a combobox that is stronly typed?
I'm using a ComboBox to display objects of a class I've defined, say CQQ.
Works great except somehow I occasionally set an Item to a String object instead of an object of type CQQ. It looks like Text replaces an item or something like that. This results in a runtime error at which time I learn that the item that should be CQQ is a String. I can't find out where or how the setting happens. It occurs to me that if the comboBox defined it's Items as objects of type CQQ instead of Object it would the usage would be less error prone and more likely to be bug free. Is there some way I could generate a strongly typed combobox? I know I could simply inherit a combobox and try to override anything the changes an Item but that leaves the possibility that I'd miss some method and not really have what I want. I'd like to just change the Items collection once. Is that possible? Thanks
Why not create a list of CQQ and then bind the combobox to it. Then to add
anything to the combobox, you'll have to add it to the list, which will blow up if you try to add an object other than a CQQ to it. Off the top of my head, something like this: Dim myList As List(Of CQQ) 'add entries to the list myList.Add(New CQQ("field1", "field2")) myList.Add(New CQQ("field1", "field2")) myList.Add(New CQQ("field1", "field2")) myComboBox.DataSource = myList myComboBox.DisplayMember = myList.field2 myComboBox.ValueMember = myList.field1 Robin S. ------------------------------------------ [quoted text, click to view] " active" <activeNOSPAM@a-znet.com> wrote in message news:uWtm6h6UHHA.480@TK2MSFTNGP02.phx.gbl... > I'm using a ComboBox to display objects of a class I've defined, say CQQ. > > Works great except somehow I occasionally set an Item to a String object > instead of an object of type CQQ. > > It looks like Text replaces an item or something like that. > > This results in a runtime error at which time I learn that the item that > should be CQQ is a String. > > I can't find out where or how the setting happens. > > It occurs to me that if the comboBox defined it's Items as objects of > type CQQ instead of Object it would the usage would be less error prone > and more likely to be bug free. > > Is there some way I could generate a strongly typed combobox? > > I know I could simply inherit a combobox and try to override anything the > changes an Item but that leaves the possibility that I'd miss some method > and not really have what I want. I'd like to just change the Items > collection once. > > Is that possible? > > > Thanks > > >
Because I know nothing about using a datasource.
I'll look into what you've given below and see if I can learn enough to use it. There is also SetItemCore and SetItemsCore that I have to look into. Thanks a lot [quoted text, click to view] "RobinS" <RobinS@NoSpam.yah.none> wrote in message news:3didnWh-p7DvtkTYnZ2dnUVZ_u-unZ2d@comcast.com... > Why not create a list of CQQ and then bind the combobox to it. Then to add > anything to the combobox, you'll have to add it to the list, which will > blow up if you try to add an object other than a CQQ to it. Off the top of > my head, something like this: > > Dim myList As List(Of CQQ) > > 'add entries to the list > myList.Add(New CQQ("field1", "field2")) > myList.Add(New CQQ("field1", "field2")) > myList.Add(New CQQ("field1", "field2")) > > myComboBox.DataSource = myList > myComboBox.DisplayMember = myList.field2 > myComboBox.ValueMember = myList.field1 > > Robin S. > ------------------------------------------ > " active" <activeNOSPAM@a-znet.com> wrote in message > news:uWtm6h6UHHA.480@TK2MSFTNGP02.phx.gbl... >> I'm using a ComboBox to display objects of a class I've defined, say CQQ. >> >> Works great except somehow I occasionally set an Item to a String object >> instead of an object of type CQQ. >> >> It looks like Text replaces an item or something like that. >> >> This results in a runtime error at which time I learn that the item that >> should be CQQ is a String. >> >> I can't find out where or how the setting happens. >> >> It occurs to me that if the comboBox defined it's Items as objects of >> type CQQ instead of Object it would the usage would be less error prone >> and more likely to be bug free. >> >> Is there some way I could generate a strongly typed combobox? >> >> I know I could simply inherit a combobox and try to override anything the >> changes an Item but that leaves the possibility that I'd miss some method >> and not really have what I want. I'd like to just change the Items >> collection once. >> >> Is that possible? >> >> >> Thanks >> >> >> > >
I've used what you suggested almost with no changes.
Below is what I've tried and it appears to be storing data but not displaying it. I've tried everything I can think of for the DisplayMember! StringWithInteger has two properties: Str and Value Public myList As List(Of StringWithInteger) = New List(Of StringWithInteger) and myList.Add(itemValue) 'itemValue is type StringWithInteger and Public Sub New() MyBase.New() InitializeComponent() Me.DataSource = myList Me.DisplayMember = myList.field2 Me.ValueMember = myList.field1 End Sub [quoted text, click to view] "RobinS" <RobinS@NoSpam.yah.none> wrote in message news:3didnWh-p7DvtkTYnZ2dnUVZ_u-unZ2d@comcast.com... > Why not create a list of CQQ and then bind the combobox to it. Then to add > anything to the combobox, you'll have to add it to the list, which will > blow up if you try to add an object other than a CQQ to it. Off the top of > my head, something like this: > > Dim myList As List(Of CQQ) > > 'add entries to the list > myList.Add(New CQQ("field1", "field2")) > myList.Add(New CQQ("field1", "field2")) > myList.Add(New CQQ("field1", "field2")) > > myComboBox.DataSource = myList > myComboBox.DisplayMember = myList.field2 > myComboBox.ValueMember = myList.field1 > > Robin S. > ------------------------------------------ > " active" <activeNOSPAM@a-znet.com> wrote in message > news:uWtm6h6UHHA.480@TK2MSFTNGP02.phx.gbl... >> I'm using a ComboBox to display objects of a class I've defined, say CQQ. >> >> Works great except somehow I occasionally set an Item to a String object >> instead of an object of type CQQ. >> >> It looks like Text replaces an item or something like that. >> >> This results in a runtime error at which time I learn that the item that >> should be CQQ is a String. >> >> I can't find out where or how the setting happens. >> >> It occurs to me that if the comboBox defined it's Items as objects of >> type CQQ instead of Object it would the usage would be less error prone >> and more likely to be bug free. >> >> Is there some way I could generate a strongly typed combobox? >> >> I know I could simply inherit a combobox and try to override anything the >> changes an Item but that leaves the possibility that I'd miss some method >> and not really have what I want. I'd like to just change the Items >> collection once. >> >> Is that possible? >> >> >> Thanks >> >> >> > >
Can you show your class definition for StringWithInteger?
Robin S. ------------------------------- [quoted text, click to view] " active" <activeNOSPAM@a-znet.com> wrote in message news:%23pXZ5LFVHHA.3592@TK2MSFTNGP03.phx.gbl... > This is the attempt that seems like it should work but I get nothing in > the drop down box even though the debugger shows myList to have 187 > items > >> StringWithInteger has two properties: Str and Value >> >> Public myList As List(Of StringWithInteger) = New List(Of >> StringWithInteger) >> >> and >> >> myList.Add(itemValue) 'itemValue is type StringWithInteger >> >> and >> >> Public Sub New() >> >> MyBase.New() >> >> InitializeComponent() > MyBase.DataSource = myList > > MyBase.DisplayMember = "Str" > > MyBase.ValueMember = "Value" > > >> End Sub > > >
This is the attempt that seems like it should work but I get nothing in the
drop down box even though the debugger shows myList to have 187 items [quoted text, click to view] > StringWithInteger has two properties: Str and Value MyBase.DataSource = myList> > Public myList As List(Of StringWithInteger) = New List(Of > StringWithInteger) > > and > > myList.Add(itemValue) 'itemValue is type StringWithInteger > > and > > Public Sub New() > > MyBase.New() > > InitializeComponent() MyBase.DisplayMember = "Str" MyBase.ValueMember = "Value" [quoted text, click to view] > End Sub
[quoted text, click to view]
On Feb 19, 3:57 pm, " active" <activeNOS...@a-znet.com> wrote: > "Cor Ligthert [MVP]" <notmyfirstn...@planet.nl> wrote in messagenews:ePfrtsGVHHA.3592@TK2MSFTNGP06.phx.gbl... > > > Active, > > > If you know nothing from a datasource, why do you than try to use it > > direct on your own usercontrol. > > > Can you not first try it as Robin show you on a normal combobox and then > > start to implement that on your own usercombobox? > > I did just that. In fact I gave the combobox properties so the form can > supply the List and set the DisplayMember and the ValueMember so the > combobox is somewhat general purpose. > > However I don't know how to "unbind" the list and then rebind it. > I need to do that because changing the list after it is bound does not > change the boxes display. > That is, how do I undo .DataSource = myList > > Thanks > > thanks > > > > > Just my thought, > > > Cor > > > " active" <activeNOS...@a-znet.com> schreef in bericht > >news:%23pXZ5LFVHHA.3592@TK2MSFTNGP03.phx.gbl... > >> This is the attempt that seems like it should work but I get nothing in > >> the drop down box even though the debugger shows myList to have 187 > >> items > > >>> StringWithInteger has two properties: Str and Value > > >>> Public myList As List(Of StringWithInteger) = New List(Of > >>> StringWithInteger) > > >>> and > > >>> myList.Add(itemValue) 'itemValue is type StringWithInteger > > >>> and > > >>> Public Sub New() > > >>> MyBase.New() > > >>> InitializeComponent() > >> MyBase.DataSource = myList > > >> MyBase.DisplayMember = "Str" > > >> MyBase.ValueMember = "Value" > > >>> End Sub Instead of using List(Of StringWithInteger), try using BindingList(Of StringWithInteger) Chris
[quoted text, click to view] "Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in message news:ePfrtsGVHHA.3592@TK2MSFTNGP06.phx.gbl... > Active, > > If you know nothing from a datasource, why do you than try to use it > direct on your own usercontrol. > > Can you not first try it as Robin show you on a normal combobox and then > start to implement that on your own usercombobox? I did just that. In fact I gave the combobox properties so the form can supply the List and set the DisplayMember and the ValueMember so the combobox is somewhat general purpose. However I don't know how to "unbind" the list and then rebind it. I need to do that because changing the list after it is bound does not change the boxes display. That is, how do I undo .DataSource = myList Thanks thanks [quoted text, click to view] > > Just my thought, > > Cor > > " active" <activeNOSPAM@a-znet.com> schreef in bericht > news:%23pXZ5LFVHHA.3592@TK2MSFTNGP03.phx.gbl... >> This is the attempt that seems like it should work but I get nothing in >> the drop down box even though the debugger shows myList to have 187 >> items >> >>> StringWithInteger has two properties: Str and Value >>> >>> Public myList As List(Of StringWithInteger) = New List(Of >>> StringWithInteger) >>> >>> and >>> >>> myList.Add(itemValue) 'itemValue is type StringWithInteger >>> >>> and >>> >>> Public Sub New() >>> >>> MyBase.New() >>> >>> InitializeComponent() >> MyBase.DataSource = myList >> >> MyBase.DisplayMember = "Str" >> >> MyBase.ValueMember = "Value" >> >> >>> End Sub >> >> >> > >
I recommend you use a BindingSource component between the data source and
the combobox. You can drag one onto the form from the Toolbox, or create it ="on the fly". Dim myBindingSource As BindingSource = New BindingSource() myBindingSource.DataSource = myList myComboBox.DataSource = myBindingSource myComboBox.ValueMember = "whatever" myComboBox.DisplayMember = "whatever" Now when you change the list, the BindingSource will respond, and then repaint the control. The BindingSource is sort of like lubrication between the data source and the control. Putting it in the middle gives you a bunch of methods and properties you can access, and better controls the bound data and the display of it. As Chris Dunaway recommended, you could define your list as a BindingList(Of T), but you would still probably want to use a BindingSource for the reason mentioned above. Give this a try, and let me know how it works. Robin S. ---------------------------- [quoted text, click to view] " active" <activeNOSPAM@a-znet.com> wrote in message news:eazAHEHVHHA.480@TK2MSFTNGP02.phx.gbl... > > "Cor Ligthert [MVP]" <notmyfirstname@planet.nl> wrote in message > news:ePfrtsGVHHA.3592@TK2MSFTNGP06.phx.gbl... >> Active, >> >> If you know nothing from a datasource, why do you than try to use it >> direct on your own usercontrol. >> >> Can you not first try it as Robin show you on a normal combobox and then >> start to implement that on your own usercombobox? > > I did just that. In fact I gave the combobox properties so the form can > supply the List and set the DisplayMember and the ValueMember so the > combobox is somewhat general purpose. > > However I don't know how to "unbind" the list and then rebind it. > I need to do that because changing the list after it is bound does not > change the boxes display. > That is, how do I undo .DataSource = myList > > Thanks > > > > > thanks > >> >> Just my thought, >> >> Cor >> >> " active" <activeNOSPAM@a-znet.com> schreef in bericht >> news:%23pXZ5LFVHHA.3592@TK2MSFTNGP03.phx.gbl... >>> This is the attempt that seems like it should work but I get nothing in >>> the drop down box even though the debugger shows myList to have 187 >>> items >>> >>>> StringWithInteger has two properties: Str and Value >>>> >>>> Public myList As List(Of StringWithInteger) = New List(Of >>>> StringWithInteger) >>>> >>>> and >>>> >>>> myList.Add(itemValue) 'itemValue is type StringWithInteger >>>> >>>> and >>>> >>>> Public Sub New() >>>> >>>> MyBase.New() >>>> >>>> InitializeComponent() >>> MyBase.DataSource = myList >>> >>> MyBase.DisplayMember = "Str" >>> >>> MyBase.ValueMember = "Value" >>> >>> >>>> End Sub >>> >>> >>> >> >> > >
I think I have a new problem now.
I don't know how to "unbind" the list and then rebind it. I need to do that because changing the list after it is bound does not change the box's display. That is, how do I undo .DataSource = myList so I can change myList and the rebind it? Thanks [quoted text, click to view] "RobinS" <RobinS@NoSpam.yah.none> wrote in message news:CeOdnaLkO5QTiUfYnZ2dnUVZ_hCdnZ2d@comcast.com... > Can you show your class definition for StringWithInteger? > I think I'm past the earlier problem now (see above) but since you asked I've added the class below. I removed some to make it easier to read. Public Class StringWithInteger Private mInteger As Integer Private mString As String Public Sub New(ByVal str As String, ByVal value As Integer) mString = str mInteger = value End Sub Public Overrides Function ToString() As String ToString = mString End Function Public Property Str() As String Get Str = mString End Get Set(ByVal text As String) mString = text End Set End Property Public Property Value() As Integer Get Value = mInteger End Get Set(ByVal numb As Integer) mInteger = numb End Set End Property End Class
Chris
[quoted text, click to view] >> Chris, Does your reply relate to the above question or to the entire >> However I don't know how to "unbind" the list and then rebind it. >> I need to do that because changing the list after it is bound does not >> change the boxes display. >> That is, how do I undo .DataSource = myList >> >> Thanks requirement? My next problem will relate to sorting the box's displayed list. Does that impact the usage of either List or BindingList Thanks [quoted text, click to view] > > Instead of using List(Of StringWithInteger), try using BindingList(Of > StringWithInteger) > > Chris >
I figured the BindingSource would fix your problem. For binding to a combobox, I think a BindingList is overkill. I use a BindingList when binding a list of my business objects to a DataGridView so I can access the methods and properties of the bindinglist and override them as needed. There's no reason for you to not use a List() if it works for you. If you are loading the combobox from a datatable, sort it when you pull it from the database. "Select LastName, FIrstName From MyCustomerTable ORDER BY Lastname, FirstName". If that's not viable, the BindingSource has sort capabilities. (See what I mean about it having methods and properties you can use? Hubba hubba.) For example, this will sort the data in my CustomersBindingSource by ContactName in Ascending order. CustomersBindingSource.Sort = "ContactName ASC" There's probably also some kind of sort property on the combobox, but I'm too tired to look it up. ;-) [quoted text, click to view] > I still make changes by changing the list. > The BindingSource doc seemed to say that changes in the data can be made > through it. Should I be looking at doing that? I think it's talking about when you want to change the data and save it back to the data source, like when you are binding the data to a DataGridView. You don't need to worry about that at this point. I'm glad it's working. Good luck. Robin S. Ts'i mahnu uterna ot twan ot geifur hingts uto. ----------------------------------------------- [quoted text, click to view] " active" <activeNOSPAM@a-znet.com> wrote in message news:%23ywQmfJVHHA.3568@TK2MSFTNGP06.phx.gbl... > To update the display, what I previously had to do was rebind the list > each time I changed the list. > That seemed to work OK. > I inserted the BindingSource as you recommended and no longer need to > rebind after changes. > Chris Dunaway didn't really recommend. He suggested I try BindingList(Of > T). I did and didn't notice any difference. > I tried reading about all the stuff you and Chris suggested - but my > background is lacking and it is pretty slow going. > So I really want to thanks you for all the help. Now at least I know what > I need to read until I understand it. > Strange to have it working and not understand what is going on. > > The List class seems a little simpler so I'd prefer to stay with that > unless there is a strong reason to use BindingList - is there such a > reason? > > I've been looking at internet sites trying to find out how to sort the > ComboBox display. Can you easily point me to something that would help? > > Thanks again for all the help! > > PS > I still make changes by changing the list. > The BindingSource doc seemed to say that changes in the data can be made > through it. Should I be looking at doing that? > > > > "RobinS" <RobinS@NoSpam.yah.none> wrote in message > news:voedne3R9q7w1UfYnZ2dnUVZ_revnZ2d@comcast.com... >>I recommend you use a BindingSource component between the data source and >>the combobox. You can drag one onto the form from the Toolbox, or create >>it ="on the fly". >> >> Dim myBindingSource As BindingSource = New BindingSource() >> >> myBindingSource.DataSource = myList >> >> myComboBox.DataSource = myBindingSource >> myComboBox.ValueMember = "whatever" >> myComboBox.DisplayMember = "whatever" >> >> Now when you change the list, the BindingSource will respond, and then >> repaint the control. The BindingSource is sort of like lubrication >> between the data source and the control. Putting it in the middle gives >> you a bunch of methods and properties you can access, and better >> controls the bound data and the display of it. >> >> As Chris Dunaway recommended, you could define your list as a >> BindingList(Of T), but you would still probably want to use a >> BindingSource for the reason mentioned above. >> >> Give this a try, and let me know how it works. >> >> Robin S. >> > >
To update the display, what I previously had to do was rebind the list each
time I changed the list. That seemed to work OK. I inserted the BindingSource as you recommended and no longer need to rebind after changes. Chris Dunaway didn't really recommend. He suggested I try BindingList(Of T). I did and didn't notice any difference. I tried reading about all the stuff you and Chris suggested - but my background is lacking and it is pretty slow going. So I really want to thanks you for all the help. Now at least I know what I need to read until I understand it. Strange to have it working and not understand what is going on. The List class seems a little simpler so I'd prefer to stay with that unless there is a strong reason to use BindingList - is there such a reason? I've been looking at internet sites trying to find out how to sort the ComboBox display. Can you easily point me to something that would help? Thanks again for all the help! PS I still make changes by changing the list. The BindingSource doc seemed to say that changes in the data can be made through it. Should I be looking at doing that? [quoted text, click to view] "RobinS" <RobinS@NoSpam.yah.none> wrote in message news:voedne3R9q7w1UfYnZ2dnUVZ_revnZ2d@comcast.com... >I recommend you use a BindingSource component between the data source and >the combobox. You can drag one onto the form from the Toolbox, or create it >="on the fly". > > Dim myBindingSource As BindingSource = New BindingSource() > > myBindingSource.DataSource = myList > > myComboBox.DataSource = myBindingSource > myComboBox.ValueMember = "whatever" > myComboBox.DisplayMember = "whatever" > > Now when you change the list, the BindingSource will respond, and then > repaint the control. The BindingSource is sort of like lubrication between > the data source and the control. Putting it in the middle gives you a > bunch of methods and properties you can access, and better controls the > bound data and the display of it. > > As Chris Dunaway recommended, you could define your list as a > BindingList(Of T), but you would still probably want to use a > BindingSource for the reason mentioned above. > > Give this a try, and let me know how it works. > > Robin S. >
Active,
If you know nothing from a datasource, why do you than try to use it direct on your own usercontrol. Can you not first try it as Robin show you on a normal combobox and then start to implement that on your own usercombobox? Just my thought, Cor " active" <activeNOSPAM@a-znet.com> schreef in bericht news:%23pXZ5LFVHHA.3592@TK2MSFTNGP03.phx.gbl... [quoted text, click to view] > This is the attempt that seems like it should work but I get nothing in > the drop down box even though the debugger shows myList to have 187 items > >> StringWithInteger has two properties: Str and Value >> >> Public myList As List(Of StringWithInteger) = New List(Of >> StringWithInteger) >> >> and >> >> myList.Add(itemValue) 'itemValue is type StringWithInteger >> >> and >> >> Public Sub New() >> >> MyBase.New() >> >> InitializeComponent() > MyBase.DataSource = myList > > MyBase.DisplayMember = "Str" > > MyBase.ValueMember = "Value" > > >> End Sub > > >
I have a feeling I'm taking advantage of you good nature, but I can't stop!
After I wrote last night, I found the SortedList generic class Which works OK and produces a sorted display. However, there is something I can't figure out: I need to get the integer part of StringWithInteger (Value) of the selected item I got this far = DirectCast(StringWithIntegerComboBox1.SelectedItem, SortedList(Of String, StringWithInteger)) StringWithInteger has two properties Str and Value I don't think I want to cast to SortedList but something like SortedList.Item That's my present problem. Thanks again I'll also try List with the sort method you pointed out but I would like to know how to do the above. a smaller problem is in understanding. I continue to use StringWithIntegerComboBox1.ItemDisplayMember = "Str" StringWithIntegerComboBox1.ItemValueMember = "Value" With List there was only one object so I could see how that might work. With SortedList there are two objects and I wonder how it finds the property It appears to find it because I tried StringWithIntegerComboBox1.ItemDisplayMember = "qqStr" StringWithIntegerComboBox1.ItemValueMember = "qqValue" and this produced an exception which makes me think that it was using the original one - not ignoring them Suppose both objects had a property "Value", then what? [quoted text, click to view] "RobinS" <RobinS@NoSpam.yah.none> wrote in message news:AIqdnahXbPtZ8EfYnZ2dnUVZ_ternZ2d@comcast.com... > > I figured the BindingSource would fix your problem. > > For binding to a combobox, I think a BindingList is overkill. I use a > BindingList when binding a list of my business objects to a DataGridView > so I can access the methods and properties of the bindinglist and override > them as needed. There's no reason for you to not use a List() if it works > for you. > > If you are loading the combobox from a datatable, sort it when you pull it > from the database. "Select LastName, FIrstName From MyCustomerTable ORDER > BY Lastname, FirstName". > > If that's not viable, the BindingSource has sort capabilities. (See what I > mean about it having methods and properties you can use? Hubba hubba.) > > For example, this will sort the data in my CustomersBindingSource by > ContactName in Ascending order. > > CustomersBindingSource.Sort = "ContactName ASC" > > There's probably also some kind of sort property on the combobox, but I'm > too tired to look it up. ;-) > >> I still make changes by changing the list. >> The BindingSource doc seemed to say that changes in the data can be made >> through it. Should I be looking at doing that? > > I think it's talking about when you want to change the data and save it > back to the data source, like when you are binding the data to a > DataGridView. You don't need to worry about that at this point. > > I'm glad it's working. Good luck. > Robin S. > Ts'i mahnu uterna ot twan ot geifur hingts uto. > ----------------------------------------------- > " active" <activeNOSPAM@a-znet.com> wrote in message > news:%23ywQmfJVHHA.3568@TK2MSFTNGP06.phx.gbl... >> To update the display, what I previously had to do was rebind the list >> each time I changed the list. >> That seemed to work OK. >> I inserted the BindingSource as you recommended and no longer need to >> rebind after changes. >> Chris Dunaway didn't really recommend. He suggested I try BindingList(Of >> T). I did and didn't notice any difference. >> I tried reading about all the stuff you and Chris suggested - but my >> background is lacking and it is pretty slow going. >> So I really want to thanks you for all the help. Now at least I know what >> I need to read until I understand it. >> Strange to have it working and not understand what is going on. >> >> The List class seems a little simpler so I'd prefer to stay with that >> unless there is a strong reason to use BindingList - is there such a >> reason? >> >> I've been looking at internet sites trying to find out how to sort the >> ComboBox display. Can you easily point me to something that would help? >> >> Thanks again for all the help! >> >> PS >> I still make changes by changing the list. >> The BindingSource doc seemed to say that changes in the data can be made >> through it. Should I be looking at doing that? >> >> >> >> "RobinS" <RobinS@NoSpam.yah.none> wrote in message >> news:voedne3R9q7w1UfYnZ2dnUVZ_revnZ2d@comcast.com... >>>I recommend you use a BindingSource component between the data source and >>>the combobox. You can drag one onto the form from the Toolbox, or create >>>it ="on the fly". >>> >>> Dim myBindingSource As BindingSource = New BindingSource() >>> >>> myBindingSource.DataSource = myList >>> >>> myComboBox.DataSource = myBindingSource >>> myComboBox.ValueMember = "whatever" >>> myComboBox.DisplayMember = "whatever" >>> >>> Now when you change the list, the BindingSource will respond, and then >>> repaint the control. The BindingSource is sort of like lubrication >>> between the data source and the control. Putting it in the middle gives >>> you a bunch of methods and properties you can access, and better >>> controls the bound data and the display of it. >>> >>> As Chris Dunaway recommended, you could define your list as a >>> BindingList(Of T), but you would still probably want to use a >>> BindingSource for the reason mentioned above. >>> >>> Give this a try, and let me know how it works. >>> >>> Robin S. >>> >> >> > >
You're on the right path with the DirectCast, but you need to cast it to the object that is in the sortedlist, not to a SortedList itself. In your sorted list, I'm assuming StringWithInteger is still a class with both fields in it. Did you try this: myItem = _ DirectCast(StringWIthIntegerComboBox1.SelectedItem, _ StringWithInteger) Debug.Print(myItem.str) Debug.Print(myItem.Value.ToString) As for the data binding, my guess would be it sorts by the first value, but it retains the list of objects (second value). So it data binds to the objects in the list, and only uses the key to sort them. Robin S. ------------------------------------------ [quoted text, click to view] " active" <activeNOSPAM@a-znet.com> wrote in message news:OcgKeNPVHHA.4828@TK2MSFTNGP05.phx.gbl... >I have a feeling I'm taking advantage of you good nature, but I can't >stop! > > After I wrote last night, I found the SortedList generic class > > Which works OK and produces a sorted display. > > However, there is something I can't figure out: > > I need to get the integer part of StringWithInteger (Value) of the > selected item > > I got this far > = DirectCast(StringWithIntegerComboBox1.SelectedItem, SortedList(Of > String, StringWithInteger)) > > StringWithInteger has two properties Str and Value > > I don't think I want to cast to SortedList but something like > SortedList.Item > > That's my present problem. > > Thanks again > > I'll also try List with the sort method you pointed out but I would like > to know how to do the above. > > > > a smaller problem is in understanding. I continue to use > > StringWithIntegerComboBox1.ItemDisplayMember = "Str" > > StringWithIntegerComboBox1.ItemValueMember = "Value" > > With List there was only one object so I could see how that might work. > > With SortedList there are two objects and I wonder how it finds the > property > > It appears to find it because I tried > > StringWithIntegerComboBox1.ItemDisplayMember = "qqStr" > > StringWithIntegerComboBox1.ItemValueMember = "qqValue" > > and this produced an exception which makes me think that it was using the > original one - not ignoring them > > Suppose both objects had a property "Value", then what? > > > > > > > > > > "RobinS" <RobinS@NoSpam.yah.none> wrote in message > news:AIqdnahXbPtZ8EfYnZ2dnUVZ_ternZ2d@comcast.com... >> >> I figured the BindingSource would fix your problem. >> >> For binding to a combobox, I think a BindingList is overkill. I use a >> BindingList when binding a list of my business objects to a DataGridView >> so I can access the methods and properties of the bindinglist and >> override them as needed. There's no reason for you to not use a List() >> if it works for you. >> >> If you are loading the combobox from a datatable, sort it when you pull >> it from the database. "Select LastName, FIrstName From MyCustomerTable >> ORDER BY Lastname, FirstName". >> >> If that's not viable, the BindingSource has sort capabilities. (See what >> I mean about it having methods and properties you can use? Hubba hubba.) >> >> For example, this will sort the data in my CustomersBindingSource by >> ContactName in Ascending order. >> >> CustomersBindingSource.Sort = "ContactName ASC" >> >> There's probably also some kind of sort property on the combobox, but >> I'm too tired to look it up. ;-) >> >>> I still make changes by changing the list. >>> The BindingSource doc seemed to say that changes in the data can be >>> made through it. Should I be looking at doing that? >> >> I think it's talking about when you want to change the data and save it >> back to the data source, like when you are binding the data to a >> DataGridView. You don't need to worry about that at this point. >> >> I'm glad it's working. Good luck. >> Robin S. >> Ts'i mahnu uterna ot twan ot geifur hingts uto. >> ----------------------------------------------- >> " active" <activeNOSPAM@a-znet.com> wrote in message >> news:%23ywQmfJVHHA.3568@TK2MSFTNGP06.phx.gbl... >>> To update the display, what I previously had to do was rebind the list >>> each time I changed the list. >>> That seemed to work OK. >>> I inserted the BindingSource as you recommended and no longer need to >>> rebind after changes. >>> Chris Dunaway didn't really recommend. He suggested I try >>> BindingList(Of T). I did and didn't notice any difference. >>> I tried reading about all the stuff you and Chris suggested - but my >>> background is lacking and it is pretty slow going. >>> So I really want to thanks you for all the help. Now at least I know >>> what I need to read until I understand it. >>> Strange to have it working and not understand what is going on. >>> >>> The List class seems a little simpler so I'd prefer to stay with that >>> unless there is a strong reason to use BindingList - is there such a >>> reason? >>> >>> I've been looking at internet sites trying to find out how to sort the >>> ComboBox display. Can you easily point me to something that would help? >>> >>> Thanks again for all the help! >>> >>> PS >>> I still make changes by changing the list. >>> The BindingSource doc seemed to say that changes in the data can be >>> made through it. Should I be looking at doing that? >>> >>> >>> >>> "RobinS" <RobinS@NoSpam.yah.none> wrote in message >>> news:voedne3R9q7w1UfYnZ2dnUVZ_revnZ2d@comcast.com... >>>>I recommend you use a BindingSource component between the data source >>>>and the combobox. You can drag one onto the form from the Toolbox, or >>>>create it ="on the fly". >>>> >>>> Dim myBindingSource As BindingSource = New BindingSource() >>>> >>>> myBindingSource.DataSource = myList >>>> >>>> myComboBox.DataSource = myBindingSource >>>> myComboBox.ValueMember = "whatever" >>>> myComboBox.DisplayMember = "whatever" >>>> >>>> Now when you change the list, the BindingSource will respond, and then >>>> repaint the control. The BindingSource is sort of like lubrication >>>> between the data source and the control. Putting it in the middle >>>> gives you a bunch of methods and properties you can access, and better >>>> controls the bound data and the display of it. >>>> >>>> As Chris Dunaway recommended, you could define your list as a >>>> BindingList(Of T), but you would still probably want to use a >>>> BindingSource for the reason mentioned above. >>>> >>>> Give this a try, and let me know how it works. >>>> >>>> Robin S. >>>> >>> >>> >> >> > >
I came up with the following for SortedList(Of String, StringWithInteger)
'ControlGenericComboBox1.SelectedItem is of type: System.Collections.Generic.KeyValuePair(Of String, .StringWithInteger) 'And has properties Key and Value and DirectCast(ControlGenericComboBox1.SelectedItem, System.Collections.Generic.KeyValuePair(Of String, StringWithInteger)).Value.Numb where Numb is a property of my class Also, ComboBox disallows sort if a datasource is used. Also, with List(Of StringWithInteger) I couldn't get the following to work. The doc's seem to say it should. BindingSource1.Sort = "Str ASC" Just occurred to me: I wonder if System.Collections.Generic.KeyValuePair applies here. Thanks for all the help [quoted text, click to view] "RobinS" <RobinS@NoSpam.yah.none> wrote in message
news:wKudndZEzIAq4UbYnZ2dnUVZ_uKknZ2d@comcast.com... > > You're on the right path with the DirectCast, but you need to cast it to > the object that is in the sortedlist, not to a SortedList itself. > > In your sorted list, I'm assuming StringWithInteger is still a class with > both fields in it. Did you try this: > > myItem = _ > DirectCast(StringWIthIntegerComboBox1.SelectedItem, _ > StringWithInteger) > > Debug.Print(myItem.str) > Debug.Print(myItem.Value.ToString) > > As for the data binding, my guess would be it sorts by the first value, > but it retains the list of objects (second value). So it data binds to the > objects in the list, and only uses the key to sort them. > > Robin S. > ------------------------------------------ > > " active" <activeNOSPAM@a-znet.com> wrote in message > news:OcgKeNPVHHA.4828@TK2MSFTNGP05.phx.gbl... >>I have a feeling I'm taking advantage of you good nature, but I can't >>stop! >> >> After I wrote last night, I found the SortedList generic class >> >> Which works OK and produces a sorted display. >> >> However, there is something I can't figure out: >> >> I need to get the integer part of StringWithInteger (Value) of the >> selected item >> >> I got this far >> = DirectCast(StringWithIntegerComboBox1.SelectedItem, SortedList(Of >> String, StringWithInteger)) >> >> StringWithInteger has two properties Str and Value >> >> I don't think I want to cast to SortedList but something like >> SortedList.Item >> >> That's my present problem. >> >> Thanks again >> >> I'll also try List with the sort method you pointed out but I would like >> to know how to do the above. >> >> >> >> a smaller problem is in understanding. I continue to use >> >> StringWithIntegerComboBox1.ItemDisplayMember = "Str" >> >> StringWithIntegerComboBox1.ItemValueMember = "Value" >> >> With List there was only one object so I could see how that might work. >> >> With SortedList there are two objects and I wonder how it finds the >> property >> >> It appears to find it because I tried >> >> StringWithIntegerComboBox1.ItemDisplayMember = "qqStr" >> >> StringWithIntegerComboBox1.ItemValueMember = "qqValue" >> >> and this produced an exception which makes me think that it was using the >> original one - not ignoring them >> >> Suppose both objects had a property "Value", then what? >> >> >> >> >> >> >> >> >> >> "RobinS" <RobinS@NoSpam.yah.none> wrote in message >> news:AIqdnahXbPtZ8EfYnZ2dnUVZ_ternZ2d@comcast.com... >>> >>> I figured the BindingSource would fix your problem. >>> >>> For binding to a combobox, I think a BindingList is overkill. I use a >>> BindingList when binding a list of my business objects to a DataGridView >>> so I can access the methods and properties of the bindinglist and >>> override them as needed. There's no reason for you to not use a List() >>> if it works for you. >>> >>> If you are loading the combobox from a datatable, sort it when you pull >>> it from the database. "Select LastName, FIrstName From MyCustomerTable >>> ORDER BY Lastname, FirstName". >>> >>> If that's not viable, the BindingSource has sort capabilities. (See what >>> I mean about it having methods and properties you can use? Hubba hubba.) >>> >>> For example, this will sort the data in my CustomersBindingSource by >>> ContactName in Ascending order. >>> >>> CustomersBindingSource.Sort = "ContactName ASC" >>> >>> There's probably also some kind of sort property on the combobox, but >>> I'm too tired to look it up. ;-) >>> >>>> I still make changes by changing the list. >>>> The BindingSource doc seemed to say that changes in the data can be >>>> made through it. Should I be looking at doing that? >>> >>> I think it's talking about when you want to change the data and save it >>> back to the data source, like when you are binding the data to a >>> DataGridView. You don't need to worry about that at this point. >>> >>> I'm glad it's working. Good luck. >>> Robin S. >>> Ts'i mahnu uterna ot twan ot geifur hingts uto. >>> ----------------------------------------------- >>> " active" <activeNOSPAM@a-znet.com> wrote in message >>> news:%23ywQmfJVHHA.3568@TK2MSFTNGP06.phx.gbl... >>>> To update the display, what I previously had to do was rebind the list >>>> each time I changed the list. >>>> That seemed to work OK. >>>> I inserted the BindingSource as you recommended and no longer need to >>>> rebind after changes. >>>> Chris Dunaway didn't really recommend. He suggested I try >>>> BindingList(Of T). I did and didn't notice any difference. >>>> I tried reading about all the stuff you and Chris suggested - but my >>>> background is lacking and it is pretty slow going. >>>> So I really want to thanks you for all the help. Now at least I know >>>> what I need to read until I understand it. >>>> Strange to have it working and not understand what is going on. >>>> >>>> The List class seems a little simpler so I'd prefer to stay with that >>>> unless there is a strong reason to use BindingList - is there such a >>>> reason? >>>> >>>> I've been looking at internet sites trying to find out how to sort the >>>> ComboBox display. Can you easily point me to something that would help? >>>> >>>> Thanks again for all the help! >>>> >>>> PS >>>> I still make changes by changing the list. >>>> The BindingSource doc seemed to say that changes in the data can be >>>> made through it. Should I be looking at doing that? >>>> >>>> >>>> >>>> "RobinS" <RobinS@NoSpam.yah.none> wrote in message >>>> news:voedne3R9q7w1UfYnZ2dnUVZ_revnZ2d@comcast.com... >>>>>I recommend you use a BindingSource component between the data source >>>>>and the combobox. You can drag one onto the form from the Toolbox, or >>>>>create it ="on the fly". >>>>> >>>>> Dim myBindingSource As BindingSource = New BindingSource() >>>>> >>>>> myBindingSource.DataSource = myList >>>>> >>>>> myComboBox.DataSource = myBindingSource >>>>> myComboBox.ValueMember = "whatever"
Now I don't know what the heck you're doing. Please post your class
definition for StringWithInteger, what you're using to create a list of them, and the code you are using to bind the combobox. Robin S. --------------------------------------------- [quoted text, click to view] " active" <activeNOSPAM@a-znet.com> wrote in message
news:ujZv6ocVHHA.4756@TK2MSFTNGP06.phx.gbl... >I came up with the following for SortedList(Of String, StringWithInteger) > > 'ControlGenericComboBox1.SelectedItem is of type: > System.Collections.Generic.KeyValuePair(Of String, .StringWithInteger) > > 'And has properties Key and Value > > and > > DirectCast(ControlGenericComboBox1.SelectedItem, > System.Collections.Generic.KeyValuePair(Of String, > StringWithInteger)).Value.Numb > > where Numb is a property of my class > > > > Also, ComboBox disallows sort if a datasource is used. > > > > Also, with > > List(Of StringWithInteger) > > I couldn't get the following to work. > > The doc's seem to say it should. > > BindingSource1.Sort = "Str ASC" > > Just occurred to me: I wonder if > > System.Collections.Generic.KeyValuePair > > applies here. > > > > Thanks for all the help > > > > > > "RobinS" <RobinS@NoSpam.yah.none> wrote in message > news:wKudndZEzIAq4UbYnZ2dnUVZ_uKknZ2d@comcast.com... >> >> You're on the right path with the DirectCast, but you need to cast it to >> the object that is in the sortedlist, not to a SortedList itself. >> >> In your sorted list, I'm assuming StringWithInteger is still a class >> with both fields in it. Did you try this: >> >> myItem = _ >> DirectCast(StringWIthIntegerComboBox1.SelectedItem, _ >> StringWithInteger) >> >> Debug.Print(myItem.str) >> Debug.Print(myItem.Value.ToString) >> >> As for the data binding, my guess would be it sorts by the first value, >> but it retains the list of objects (second value). So it data binds to >> the objects in the list, and only uses the key to sort them. >> >> Robin S. >> ------------------------------------------ >> >> " active" <activeNOSPAM@a-znet.com> wrote in message >> news:OcgKeNPVHHA.4828@TK2MSFTNGP05.phx.gbl... >>>I have a feeling I'm taking advantage of you good nature, but I can't >>>stop! >>> >>> After I wrote last night, I found the SortedList generic class >>> >>> Which works OK and produces a sorted display. >>> >>> However, there is something I can't figure out: >>> >>> I need to get the integer part of StringWithInteger (Value) of the >>> selected item >>> >>> I got this far >>> = DirectCast(StringWithIntegerComboBox1.SelectedItem, SortedList(Of >>> String, StringWithInteger)) >>> >>> StringWithInteger has two properties Str and Value >>> >>> I don't think I want to cast to SortedList but something like >>> SortedList.Item >>> >>> That's my present problem. >>> >>> Thanks again >>> >>> I'll also try List with the sort method you pointed out but I would >>> like to know how to do the above. >>> >>> >>> >>> a smaller problem is in understanding. I continue to use >>> >>> StringWithIntegerComboBox1.ItemDisplayMember = "Str" >>> >>> StringWithIntegerComboBox1.ItemValueMember = "Value" >>> >>> With List there was only one object so I could see how that might work. >>> >>> With SortedList there are two objects and I wonder how it finds the >>> property >>> >>> It appears to find it because I tried >>> >>> StringWithIntegerComboBox1.ItemDisplayMember = "qqStr" >>> >>> StringWithIntegerComboBox1.ItemValueMember = "qqValue" >>> >>> and this produced an exception which makes me think that it was using >>> the original one - not ignoring them >>> >>> Suppose both objects had a property "Value", then what? >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> "RobinS" <RobinS@NoSpam.yah.none> wrote in message >>> news:AIqdnahXbPtZ8EfYnZ2dnUVZ_ternZ2d@comcast.com... >>>> >>>> I figured the BindingSource would fix your problem. >>>> >>>> For binding to a combobox, I think a BindingList is overkill. I use a >>>> BindingList when binding a list of my business objects to a >>>> DataGridView so I can access the methods and properties of the >>>> bindinglist and override them as needed. There's no reason for you to >>>> not use a List() if it works for you. >>>> >>>> If you are loading the combobox from a datatable, sort it when you >>>> pull it from the database. "Select LastName, FIrstName From >>>> MyCustomerTable ORDER BY Lastname, FirstName". >>>> >>>> If that's not viable, the BindingSource has sort capabilities. (See >>>> what I mean about it having methods and properties you can use? Hubba >>>> hubba.) >>>> >>>> For example, this will sort the data in my CustomersBindingSource by >>>> ContactName in Ascending order. >>>> >>>> CustomersBindingSource.Sort = "ContactName ASC" >>>> >>>> There's probably also some kind of sort property on the combobox, but >>>> I'm too tired to look it up. ;-) >>>> >>>>> I still make changes by changing the list. >>>>> The BindingSource doc seemed to say that changes in the data can be >>>>> made through it. Should I be looking at doing that? >>>> >>>> I think it's talking about when you want to change the data and save >>>> it back to the data source, like when you are binding the data to a >>>> DataGridView. You don't need to worry about that at this point. >>>> >>>> I'm glad it's working. Good luck. >>>> Robin S. >>>> Ts'i mahnu uterna ot twan ot geifur hingts uto. >>>> ----------------------------------------------- >>>> " active" <activeNOSPAM@a-znet.com> wrote in message >>>> news:%23ywQmfJVHHA.3568@TK2MSFTNGP06.phx.gbl... >>>>> To update the display, what I previously had to do was rebind the >>>>> list each time I changed the list. >>>>> That seemed to work OK. >>>>> I inserted the BindingSource as you recommended and no longer need to >>>>> rebind after changes. >>>>> Chris Dunaway didn't really recommend. He suggested I try >>>>> BindingList(Of T). I did and didn't notice any difference. >>>>> I tried reading about all the stuff you and Chris suggested - but my >>>>> background is lacking and it is pretty slow going. >>>>> So I really want to thanks you for all the help. Now at least I know >>>>> what I need to read until I understand it. >>>>> Strange to have it working and not understand what is going on. >>>>> >>>>> The List class seems a little simpler so I'd prefer to stay with that >>>>> unless there is a strong reason to use BindingList - is there such a >>>>> reason? >>>>> >>>>> I've been looking at internet sites trying to find out how to sort >>>>> the ComboBox display. Can you easily point me to something that would >>>>> help? >>>>> >>>>> Thanks again for all the help! >>>>> >>>>> PS >>>>> I still make changes by changing the list. >>>>> The BindingSource doc seemed to say that changes in the data can be
I've been trying both List and SortedList
The below DirectCast is for SortedList and it works well so I thought I include it in case someone else needed it. I've posted the code for StringWithInteger and your prior help related correctly to that and List. I should have mentioned in the last post that the DirectCast pertained to SortedList, not List. It would have been nice to find out why my Sort does not work with List but I leave that for another time. I'm ready to move on, thanks to your help. [quoted text, click to view] "RobinS" <RobinS@NoSpam.yah.none> wrote in message news:UNOdna8TdJPSskDYnZ2dnUVZ_u-unZ2d@comcast.com... > Now I don't know what the heck you're doing. Please post your class > definition for StringWithInteger, what you're using to create a list of > them, and the code you are using to bind the combobox. > > Robin S. > --------------------------------------------- > " active" <activeNOSPAM@a-znet.com> wrote in message > news:ujZv6ocVHHA.4756@TK2MSFTNGP06.phx.gbl... >>I came up with the following for SortedList(Of String, StringWithInteger) >> >> 'ControlGenericComboBox1.SelectedItem is of type: >> System.Collections.Generic.KeyValuePair(Of String, .StringWithInteger) >> >> 'And has properties Key and Value >> >> and >> >> DirectCast(ControlGenericComboBox1.SelectedItem, >> System.Collections.Generic.KeyValuePair(Of String, >> StringWithInteger)).Value.Numb >> >> where Numb is a property of my class >> >> >> Also, with >> >> List(Of StringWithInteger) >> >> I couldn't get the following to work. >> >> The doc's seem to say it should. >> >> BindingSource1.Sort = "Str ASC" >>
You're welcome. I'm glad you got it to work for you.
Robin S. ------------------------------ [quoted text, click to view] " active" <activeNOSPAM@a-znet.com> wrote in message news:%23vwEIWoVHHA.4568@TK2MSFTNGP02.phx.gbl... > I've been trying both List and SortedList > The below DirectCast is for SortedList and it works well so I thought I > include it in case someone else needed it. > > I've posted the code for StringWithInteger and your prior help related > correctly to that and List. > I should have mentioned in the last post that the DirectCast pertained to > SortedList, not List. > It would have been nice to find out why my Sort does not work with List > but I leave that for another time. > I'm ready to move on, thanks to your help. > > > > "RobinS" <RobinS@NoSpam.yah.none> wrote in message > news:UNOdna8TdJPSskDYnZ2dnUVZ_u-unZ2d@comcast.com... >> Now I don't know what the heck you're doing. Please post your class >> definition for StringWithInteger, what you're using to create a list of >> them, and the code you are using to bind the combobox. >> >> Robin S. >> --------------------------------------------- >> " active" <activeNOSPAM@a-znet.com> wrote in message >> news:ujZv6ocVHHA.4756@TK2MSFTNGP06.phx.gbl... >>>I came up with the following for SortedList(Of String, >>>StringWithInteger) >>> >>> 'ControlGenericComboBox1.SelectedItem is of type: >>> System.Collections.Generic.KeyValuePair(Of String, .StringWithInteger) >>> >>> 'And has properties Key and Value >>> >>> and >>> >>> DirectCast(ControlGenericComboBox1.SelectedItem, >>> System.Collections.Generic.KeyValuePair(Of String, >>> StringWithInteger)).Value.Numb >>> >>> where Numb is a property of my class >>> > >>> >>> Also, with >>> >>> List(Of StringWithInteger) >>> >>> I couldn't get the following to work. >>> >>> The doc's seem to say it should. >>> >>> BindingSource1.Sort = "Str ASC" >>> > >
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