Redraw ComboBox [C #].

Redraw ComboBox [C #]

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By chance, I found out that override
The onpaint of ComboBox will not be called. Therefore, ComboBox cannot be re-painted like a common control.

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We can rewrite the Window Process (wndproc) to process messages.

Create a class that inherits from ComboBox,

Class customecombobox: ComboBox

 

 

 

 

[C-sharp]
View plaincopyprint?

1. // Import API functions
2. [System. runtime. interopservices. dllimport ("user32.dll")]
3. Static extern intptr getwindowdc (intptr hwnd); // return the device environment of the window specified by the hwnd parameter.
5. [System. runtime. interopservices. dllimport ("user32.dll")]
6. Static extern int releasedc (intptr hwnd, intptr HDC); // function to release the device context (DC)
8. Protected override void wndproc (ref message m)
9. {
10. Base. wndproc (ref m );
11. // Wm_paint = 0xf; requires a window to redraw itself, that is, when the painting event
12. // Wm_ctlcoloredit = 0x133; send this message to its parent window when an edit control is to be drawn;
13. // In response to this message, the owner window can set the text and background color of the edit box by using the handle of the specified display device.
14. // Windows message value table, see: http://hi.baidu.com/dooy/blog/item/0e770a24f70e3b2cd407421b.html
15. If (M. MSG = 0xf | M. MSG = 0x133)
16. {
17. Intptr HDC = getwindowdc (M. hwnd );
18. If (HDC. toint32 () = 0) // if the device context fails to be retrieved, the system returns
19. {
20. Return;
21. }
23. // Create a graphics image
24. Graphics G = graphics. fromhdc (HDC );
25. // Border
26. Controlpaint. drawborder (G, new rectangle (0, 0, width, height), color. Red, buttonborderstyle. Solid );
27. // Draw a solid line
28. Controlpaint. drawborder (G, new rectangle (width-height, 0, height, height), color. Red, buttonborderstyle. Solid );
29. // G. drawline (new pen (brushes. blue, 2), new pointf (this. width-this. height, 0), new pointf (this. width-this. height, this. height ));
30. // Release the DC
31. Releasedc (M. hwnd, HDC );
32. }
33. }

// Import the API function [system. runtime. interopservices. dllimport ("user32.dll")] Static extern intptr getwindowdc (intptr hwnd); // return the device environment of the window specified by the hwnd parameter. [System. runtime. interopservices. dllimport ("user32.dll")] Static extern int releasedc (intptr hwnd, intptr HDC); // function release device context environment (DC) protected override void wndproc (ref message m) {base. wndproc (ref m); // wm_paint = 0xf; requires a window to re-paint itself, that is, when the painting event // wm_ctlcoloredit = 0x133; the parent window to which the message is sent when an edit control is to be drawn; // The parent window to which the message is sent, the owner window can set the text and background color of the edit box by using a given handle to the relevant display device // Windows message value table, see: http://hi.baidu.com/dooy/blog/item/0e770a24f70e3b2cd407421b.html if (M. MSG = 0xf | M. MSG = 0x133) {intptr HDC = getwindowdc (M. hwnd); If (HDC. toint32 () = 0) // if the device context fails to be retrieved, {return;} // create a graphics peer image graphics G = graphics. fromhdc (HDC); // draw the controlpaint of the border. drawborder (G, new rectangle (0, 0, width, height), color. red, buttonborderstyle. solid); // draw a solid controlpaint. drawborder (G, new rectangle (width-height, 0, height, height), color. red, buttonborderstyle. solid); // G. drawline (new pen (brushes. blue, 2), new pointf (this. width-this. height, 0), new pointf (this. width-this. height, this. height); // release the DC releasedc (M. hwnd, HDC );}}

Note: This article references the http://topic.csdn.net/u/20070728/01/7e5ebf43-fce8-4db1-a05c-d44c612d1391.html

 

 

From: http://blog.csdn.net/sugar_tiger/article/details/4900641