Request help for 2 newbie questions

Wizard_01

bouli wrote: 1) What is the equivalent of Win32 GetSysColor() function in .NET? It is System.Drawing.SystemColors class bouli wrote: 2) I would like to have the equivalent in C# (.NET) of the following C++ (MFC) statement: class CMyWindow : public CWnd { ... } While CWnd is an MFC class that represents a basic window. I want to write my own control and use it Use System.Windows.Forms.Form for forms(dialogs). But for controls like button, user-controls use System.Windows.Forms.UserControl or Control. Here big difference between MFC and .NET. In MFC can be CWnd dialog and control(I used these for nested dialogs - one dialog owns another), but in .NET only classes delivered from System.Windows.Forms.Form can be dialogs and cannot contain any forms. Wizard_01

bouli

ok for System.Drawing.SystemColors... But I don't get it for the derived control. What I wanna do is to write my own control that will get some methods. these methods will control the drawing.

Mazdak

bouli wrote: What I wanna do is to write my own control that will get some methods. these methods will control the drawing

public class myControl : System.Windows.Forms.UserControl
{
public myControl()
{
}
....

private void Control_Paint(object sender,PaintEventHandler e)
{
//do drawing
}
}

Mazy No sig. available now.

bouli

ok, thanks! :D

bouli

Hi, Just one last question about this thread... Can you show me how can I use the control in the main form? I have inserted a label and? how can I link it to my new control? Best regards. Thanks.

Mazdak

bouli wrote: I have inserted a label and? how can I link it to my new control? What do you mean exactly? You mean you add that label to your UserControl? It is now in your .cs file as a private member. You can use it like this there:

lbale1.Text = "Hello";

User the search textbox at the top of this page to find articles in this site about UserControl for motr information. Mazy No sig. available now.

bouli

I want to use my new created control... this control graphically shows the content of an array ;)

Mazdak

bouli wrote: I want to use my new created control Right click on your ToolBox and select 'Customize ToolBox' option. From .NET Component tab, with Browse button , select assembly of your control and click OK. It is now added to your toolbox and you can drag and drop it on your form. Mazy No sig. available now.

Heath Stewart

For one thing, you didn't hook-up your Paint event handlers. Remember, he's a n00b. Also, never use events in a derived class - it's too slow and doesn't provide the control you might need (such as NOT calling the base class's OnPaint handler). Instead, always override the related method for an event when deriving from a class:

public class MyControl : UserControl
{
public MyControl()
{
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e); // Allows base class to paint and raise the Paint event.
// Draw
}
}

-----BEGIN GEEK CODE BLOCK----- Version: 3.21 GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++ -----END GEEK CODE BLOCK-----

Mazdak

Heath Stewart wrote: protected override void OnPaint(PaintEventArgs e) { base.OnPaint(e); // Allows base class to paint and raise the Paint event. // Draw } Yah, Thanks for correction. :) Mazy No sig. available now.

bouli

Ok, it works!! Thanks :D

bouli

ok I understood how to use and draw my own controls in C# :D It's very different from MFC...

bouli

Ok, it works that way... it's almost like MFC... just override the event...;P

Heath Stewart

Point of clarification: OnPaint is not an event. It's a method that, in the defining class, raises the Paint event before or after optionally performing some action (like any default painting). When you override this, you pre-empt the event being raised (which is why you call base.OnPaint) and actually override all the functionality of that method since it's virtual. If you don't call base.OnPaint, any painting that the base class, or its base class, etc., need to do won't be performed. For more information about events in delegates in .NET, see Handling and Raising Events[^] in the MSDN Online Library.

-----BEGIN GEEK CODE BLOCK----- Version: 3.21 GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++ -----END GEEK CODE BLOCK-----

bouli

Ok, thanks for the explainations :) Thanks :)

TuringTest1

Heath, why are events in a derived class too slow? First, i'm assuming the fact it's derived is a nonissue, your point is just that OnPaint is exposed directly for that purpose-- let me know if i misunderstand this. But why would events be slow, aren't they just callbacks? TIA. ________________________________________ Gosh, it would be awful pleas'n, to reason out the reason, for things I can't explain. Then perhaps I'd deserve ya, and be even worthy of ya.. if I only had a brain!

Heath Stewart

Consider this: when you override such a method like OnPaint, the CLR will call your virtual method which uses the callvirt (as opposed to call) IL instruction. This is polymorphism. This one call does it all. When you instead handle an event in the derived class from the base class (like handling the Paint) event, there are several IL instructions (both in your implementation and in the event's add and remove accessors, not to mention whatever they require to add the handler to the callback chain) just to wire-up the event! When the event is fired, the collection of handlers is enumerated and each one is invoked with takes several more IL instructions (some to enumerate and jump back, and a couple to invoke the delegate). I hope this makes sense. Besides, when you override the event handler like OnPaint, you don't need to know the sender because the current instance of your class is the sender. All you need is the EventArgs (or derivative, like PaintEventArgs). It simplifies your class.

Microsoft MVP, Visual C# My Articles