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dotnet compact framework
group:do we need to dispose screen controls?
dotnet compact framework:
hi there,
i use vs2005, c# and .netcf2. i know that i have to explicitly dispose any controls and components which created by myself. but how about those controls, e.g. button, which drew by c# on the screen. as a good practice, should i dispose them explicitly? or c# already does it for me with the system generated code? where is the code? i know they will be handled eventually by GC but it does not guaranteed. thanks
If they are part of the Controls collection in a Form, then the Form will
dispose of them for you. -- Chris Tacke, eMVP Join the Embedded Developer Community http://community.opennetcf.com [quoted text, click to view] "Batterhead" <batterheadccw@gmail.com> wrote in message news:a8886c2a-6157-475f-9f44-00339e7c1493@e23g2000prf.googlegroups.com... > hi there, > > i use vs2005, c# and .netcf2. i know that i have to explicitly dispose > any controls and components which created by myself. but how about > those controls, e.g. button, which drew by c# on the screen. as a good > practice, should i dispose them explicitly? or c# already does it for > me with the system generated code? where is the code? > > i know they will be handled eventually by GC but it does not > guaranteed. > > thanks > batterhead
Just ensure you call dispose on your form. It is good practice to use the
using statement. ie: in C#: using (MyForm form = new MyForm()) { form.ShowDialog(); } When control leaves the above block, the CLR will call Dispose on that form. When creating a form via the Wizard, it will override the Dispose method of the Component class and call Dispose on this for you. It overrides to clean up the components object and so you can place stuff in there if you want. You can find this in the designer partial class. ie MyForm.designer.cs. -- Simon Hart Visual Developer - Device Application Development MVP http://simonrhart.blogspot.com [quoted text, click to view] "Batterhead" wrote:
> hi there, > > i use vs2005, c# and .netcf2. i know that i have to explicitly dispose > any controls and components which created by myself. but how about > those controls, e.g. button, which drew by c# on the screen. as a good > practice, should i dispose them explicitly? or c# already does it for > me with the system generated code? where is the code? > > i know they will be handled eventually by GC but it does not > guaranteed. > > thanks > batterhead
IIRC, The using keyword isn't available until CF 2.0 (Studio '05).
-- Chris Tacke, eMVP Join the Embedded Developer Community http://community.opennetcf.com [quoted text, click to view] "Hilton" <nospam@nospam.com> wrote in message news:hp3bj.32302$JD.4986@newssvr21.news.prodigy.net... > Simon Hart wrote: >> Just ensure you call dispose on your form. It is good practice to use the >> using statement. ie: in C#: >> >> using (MyForm form = new MyForm()) >> { >> form.ShowDialog(); >> } > > This doesn't compile, at least for me anyway (VS2003) > > using (Form form = new Form ()) > {} > > Also, "(new Form () is IDisposable)" is false. > > What am I doing wrong? > > Hilton > >
[quoted text, click to view]
Simon Hart wrote: > Just ensure you call dispose on your form. It is good practice to use the > using statement. ie: in C#: > > using (MyForm form = new MyForm()) > { > form.ShowDialog(); > } This doesn't compile, at least for me anyway (VS2003) using (Form form = new Form ()) {} Also, "(new Form () is IDisposable)" is false. What am I doing wrong? Hilton
I just checked CF 1.0, 2.0 and 3.5 with Reflector and a Form is definitely
derived from IDisposable in all three. Form->ContainerControl->ScrollableControl->Control->Component->IComponent->IDisposable -- Chris Tacke, eMVP Join the Embedded Developer Community http://community.opennetcf.com [quoted text, click to view] "Hilton" <nospam@nospam.com> wrote in message news:0Bgbj.84380$YL5.41217@newssvr29.news.prodigy.net... > Chris, > > "using" is definitely a 1.0 keyword. I use it all the time; e.g. "using > (StreamReader sr = new StreamReader (...))". The problem is that Form > does not implement IDisposable on CF 1. Now if Form all of a sudden does > implement IDisposable, then that is, by Microsoft's definition, "a > breaking change" and should not be done. > > "(new Form () is IDisposable) return false on CF 1.0, but true on .NET > (desktop). > > Interesting... Seems like a major screwup/oversight by Microsoft. Yes? > > That's why I still think that the GC should have: "if o implements > IDisposable && (!o.Disposed) then o.Dispose" (pseudo code). But I was > shot down last time and I guess I will be again. So, Form does not > implement IDisposable on the Compact Framework - solve that. If it is in > CF 2.0, that is a breaking change and should not be done (according to > Microsoft). > > Comments? > > Hilton > > > > "<ctacke/>" <ctacke[at]opennetcf[dot]com> wrote in message > news:Ozvrp0JRIHA.2376@TK2MSFTNGP02.phx.gbl... >> IIRC, The using keyword isn't available until CF 2.0 (Studio '05). >> >> >> -- >> >> Chris Tacke, eMVP >> Join the Embedded Developer Community >> http://community.opennetcf.com >> >> >> >> >> "Hilton" <nospam@nospam.com> wrote in message >> news:hp3bj.32302$JD.4986@newssvr21.news.prodigy.net... >>> Simon Hart wrote: >>>> Just ensure you call dispose on your form. It is good practice to use >>>> the >>>> using statement. ie: in C#: >>>> >>>> using (MyForm form = new MyForm()) >>>> { >>>> form.ShowDialog(); >>>> } >>> >>> This doesn't compile, at least for me anyway (VS2003) >>> >>> using (Form form = new Form ()) >>> {} >>> >>> Also, "(new Form () is IDisposable)" is false. >>> >>> What am I doing wrong? >>> >>> Hilton >>> >>> >> >> > >
Chris,
[quoted text, click to view] >I just checked CF 1.0, 2.0 and 3.5 with Reflector and a Form is definitely >derived from IDisposable in all three. > > Form->ContainerControl->ScrollableControl->Control->Component->IComponent->IDisposable OK, so: Q1: Why does: using (Form form = new Form()) {} give the following compiler error: c:\test\FormDispose\Form1.cs(32): Cannot implicitly convert type 'System.Windows.Forms.Form' to 'System.IDisposable' ....and.. Q2: Why does: "(new Form () is IDisposable)" return false? Q1 is a compile time check, Q2 is a run-time and they're consistent. Hilton
To follow-up my own post:
When I run (FormDispose.exe) with the line: "MessageBox.Show (((new Form () is IDisposable).ToString()));" it returns *false*. This is using CF 1. Then I add the file FormDispose.exe.config so that FormDispose uses CF 2 and guess what? Yip, it returns *true*. Believe it, or not... Hilton [quoted text, click to view] "Hilton" <nospam@nospam.com> wrote in message news:IRmbj.784$6%.53@nlpi061.nbdc.sbc.com... > Chris, > >>I just checked CF 1.0, 2.0 and 3.5 with Reflector and a Form is definitely >>derived from IDisposable in all three. >> >> Form->ContainerControl->ScrollableControl->Control->Component->IComponent->IDisposable > > OK, so: > > Q1: Why does: > > using (Form form = new Form()) {} > > give the following compiler error: > > c:\test\FormDispose\Form1.cs(32): Cannot implicitly convert type > 'System.Windows.Forms.Form' to 'System.IDisposable' > > > ...and.. > > Q2: Why does: "(new Form () is IDisposable)" return false? > > Q1 is a compile time check, Q2 is a run-time and they're consistent. > > Hilton > >
Chris,
"using" is definitely a 1.0 keyword. I use it all the time; e.g. "using (StreamReader sr = new StreamReader (...))". The problem is that Form does not implement IDisposable on CF 1. Now if Form all of a sudden does implement IDisposable, then that is, by Microsoft's definition, "a breaking change" and should not be done. "(new Form () is IDisposable) return false on CF 1.0, but true on .NET (desktop). Interesting... Seems like a major screwup/oversight by Microsoft. Yes? That's why I still think that the GC should have: "if o implements IDisposable && (!o.Disposed) then o.Dispose" (pseudo code). But I was shot down last time and I guess I will be again. So, Form does not implement IDisposable on the Compact Framework - solve that. If it is in CF 2.0, that is a breaking change and should not be done (according to Microsoft). Comments? Hilton [quoted text, click to view] "<ctacke/>" <ctacke[at]opennetcf[dot]com> wrote in message news:Ozvrp0JRIHA.2376@TK2MSFTNGP02.phx.gbl... > IIRC, The using keyword isn't available until CF 2.0 (Studio '05). > > > -- > > Chris Tacke, eMVP > Join the Embedded Developer Community > http://community.opennetcf.com > > > > > "Hilton" <nospam@nospam.com> wrote in message > news:hp3bj.32302$JD.4986@newssvr21.news.prodigy.net... >> Simon Hart wrote: >>> Just ensure you call dispose on your form. It is good practice to use >>> the >>> using statement. ie: in C#: >>> >>> using (MyForm form = new MyForm()) >>> { >>> form.ShowDialog(); >>> } >> >> This doesn't compile, at least for me anyway (VS2003) >> >> using (Form form = new Form ()) >> {} >> >> Also, "(new Form () is IDisposable)" is false. >> >> What am I doing wrong? >> >> Hilton >> >> > >
Well you have to believe the runtime. I can only conclude that I'm looking
at the wrong 1.0 binary (or at least not the one your system is using). What version of 1.0 are you running? -- Chris Tacke, eMVP Join the Embedded Developer Community http://community.opennetcf.com [quoted text, click to view] "Hilton" <nospam@nospam.com> wrote in message news:sunbj.790$6%.199@nlpi061.nbdc.sbc.com... > To follow-up my own post: > > When I run (FormDispose.exe) with the line: > > "MessageBox.Show (((new Form () is IDisposable).ToString()));" > > it returns *false*. This is using CF 1. > > Then I add the file FormDispose.exe.config so that FormDispose uses CF 2 > and guess what? Yip, it returns *true*. > > Believe it, or not... > > Hilton > > > > "Hilton" <nospam@nospam.com> wrote in message > news:IRmbj.784$6%.53@nlpi061.nbdc.sbc.com... >> Chris, >> >>>I just checked CF 1.0, 2.0 and 3.5 with Reflector and a Form is >>>definitely derived from IDisposable in all three. >>> >>> Form->ContainerControl->ScrollableControl->Control->Component->IComponent->IDisposable >> >> OK, so: >> >> Q1: Why does: >> >> using (Form form = new Form()) {} >> >> give the following compiler error: >> >> c:\test\FormDispose\Form1.cs(32): Cannot implicitly convert type >> 'System.Windows.Forms.Form' to 'System.IDisposable' >> >> >> ...and.. >> >> Q2: Why does: "(new Form () is IDisposable)" return false? >> >> Q1 is a compile time check, Q2 is a run-time and they're consistent. >> >> Hilton >> >> > >
CF 1.0.4292.0 which is CF1 SP3
Try it, create a Pocket PC, add the line below and on CF 1, it shows false (and using doesn't compile either). Hilton [quoted text, click to view] "<ctacke/>" <ctacke[at]opennetcf[dot]com> wrote in message news:O7fOM8kRIHA.5164@TK2MSFTNGP03.phx.gbl... > Well you have to believe the runtime. I can only conclude that I'm > looking at the wrong 1.0 binary (or at least not the one your system is > using). What version of 1.0 are you running? > > > -- > > Chris Tacke, eMVP > Join the Embedded Developer Community > http://community.opennetcf.com > > > > > "Hilton" <nospam@nospam.com> wrote in message > news:sunbj.790$6%.199@nlpi061.nbdc.sbc.com... >> To follow-up my own post: >> >> When I run (FormDispose.exe) with the line: >> >> "MessageBox.Show (((new Form () is IDisposable).ToString()));" >> >> it returns *false*. This is using CF 1. >> >> Then I add the file FormDispose.exe.config so that FormDispose uses CF 2 >> and guess what? Yip, it returns *true*. >> >> Believe it, or not... >> >> Hilton >> >> >> >> "Hilton" <nospam@nospam.com> wrote in message >> news:IRmbj.784$6%.53@nlpi061.nbdc.sbc.com... >>> Chris, >>> >>>>I just checked CF 1.0, 2.0 and 3.5 with Reflector and a Form is >>>>definitely derived from IDisposable in all three. >>>> >>>> Form->ContainerControl->ScrollableControl->Control->Component->IComponent->IDisposable >>> >>> OK, so: >>> >>> Q1: Why does: >>> >>> using (Form form = new Form()) {} >>> >>> give the following compiler error: >>> >>> c:\test\FormDispose\Form1.cs(32): Cannot implicitly convert type >>> 'System.Windows.Forms.Form' to 'System.IDisposable' >>> >>> >>> ...and.. >>> >>> Q2: Why does: "(new Form () is IDisposable)" return false? >>> >>> Q1 is a compile time check, Q2 is a run-time and they're consistent. >>> >>> Hilton >>> >>> >> >> > >
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