dotnet windows forms databinding: I have created a Component called a BOConnector that implements IBindingList
so it can provide access to a list of business objects to be bound to
controls.

At design time there is no live list of objects so BOConnector creates an
internal list of one object. It needs one object because when you bind to a
grid etc at design time it needs to get a list of properties to make the
columns.

My BOConnector works just fine with grids and simple controls like edit
boxes but I have a problem with the ListBox and ComboBox.

When I connect the BOConnector to the ListBox.DataSource it seems to create
a copy of the internal business object and try to save it into its
ListBox.Items in the form definition. I seem to see what is going on here,
it is taking a copy of the data and loading it into its Items. But why is
it doing this at design time? And the complex nature of my business object
means this messes up the form totally.

My first thought is to create a descendant of the ListBox and ComboBox and
make sure it does not copy items from the DataSource to the Items list at
design time.

Has anyone got any ideas?


--
Andrew Cutforth - AJC Software - www.ajcsoft.com
The best folder synchronize and directory compare tool available.
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Here is the solution. A ListBox descendant that maintains its own data
source connection and only allows the base control to see it a run time.
This then fixes what I beleive to be a bug, the list box cannot grab the
data at design time. This also works exactly the same for ComboBox

[ToolboxBitmap(typeof(ListBox))]
public class AdvancedListBox : ListBox
{
private Object _DataSource;
[TypeConverter("System.Windows.Forms.Design.DataSourceConverter,System.Design")]
public new Object DataSource
{
get
{
return _DataSource;
}
set
{
_DataSource = value;

if (!DesignMode)
base.DataSource = value;
}
}

[DefaultValue("")]
private string _DisplayMember = string.Empty;
[TypeConverter("System.Windows.Forms.Design.DataMemberConverter,System.Design")]
public new string DisplayMember
{
get
{
return _DisplayMember;
}
set
{
_DisplayMember = value;

if (!DesignMode)
base.DisplayMember = value;
}
}

[DefaultValue("")]
private string _ValueMember = string.Empty;
[TypeConverter("System.Windows.Forms.Design.DataMemberConverter,System.Design")]
public new string ValueMember
{
get
{
return _ValueMember;
}
set
{
_ValueMember = value;

if (!DesignMode)
base.ValueMember = value;
}
}
}

--
Andrew Cutforth - AJC Software - www.ajcsoft.com
The best folder synchronize and directory compare tool available.
AJC Active Backup instantly archives every file you edit giving you
unlimited undo and automatic revision control. Never lose your data again.