Re: CreateGraphics Problem - C# Discussion Boards

1-Apr-04 10:40

VS.NET doesn't let you reference a .exe. It is possible, but you'll have to use the command line compiler (csc.exe) or a build tool like NAnt[^].

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CreateGraphics Problem

Tristan Rhodes1-Apr-04 10:25

Re: CreateGraphics Problem

1-Apr-04 10:25

I figure that to draw my little windows style borders, i need to actualy have a valid handle to the grahics device for the control.

Now, I have this section of code i have included in my component constructor that causes a problem:

Graphics clientDC = this.CreateGraphics(); <br />
IntPtr hdc = clientDC.GetHdc(); <br />
pDC = ThemeAPI.CreateCompatibleDC(hdc);<br />
clientDC.Dispose();

That throws the following error on run time:

An unhandled exception of type 'System.InvalidOperationException' occurred in system.drawing.dll

Additional information: The object is currently in use elsewhere.

Now, i know it's caused by the existence of the ClientDC, but i'm not sure how to go about solving this one.

I need to get the creatgraphics for the component in question, but I guess, as i'm creating three duplicate components at initialisation, it's running three seperate threads at once, and it's not liking the use of the Device Context. If i don't dispose of it, the program runs for a while before crashing.

Should I construct a graphics handle in the parent form?

Cata

Heath Stewart1-Apr-04 10:39

Re: CreateGraphics Problem

1-Apr-04 10:39

Call clientDC.ReleaseHdc(pDC) when you're done with the HDC, then dispose your Graphics object.

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Tristan Rhodes1-Apr-04 10:50

Re: CreateGraphics Problem

1-Apr-04 10:50

Okey dokey, works now.

I was trying to use P/Invoke DeleteDC(pDC). It clearly wasn't happy with that.

But i've still got nothing drawn on my background. I think i have the object values right, and i've tried a number of values for iState. So i'm not entirely sure why nothing is appearing. Here is the code

<br />
			pTHEME = ThemeAPI.OpenThemeData(this.Handle,"Window");<br />
<br />
			Graphics clientDC = this.CreateGraphics(); <br />
			IntPtr hdc = clientDC.GetHdc(); <br />
			pDC = ThemeAPI.CreateCompatibleDC(hdc);<br />
<br />
			//Build content Pane<br />
			ThemeAPI.Rect rect = new ThemeAPI.Rect();<br />
			rect.left = this.Location.X;<br />
			rect.top = this.Location.Y;<br />
			rect.right = this.Location.X + this.Size.Width;<br />
			rect.bottom = this.Location.Y + this.Size.Height;<br />
<br />
			int result;<br />
			//Draw Background<br />
			result = ThemeAPI.DrawThemeBackground(pTHEME,pDC,5,1,ref rect,IntPtr.Zero);<br />
			result = ThemeAPI.DrawThemeBackground(pTHEME,pDC,7,1,ref rect,IntPtr.Zero);<br />
			result = ThemeAPI.DrawThemeBackground(pTHEME,pDC,8,1,ref rect,IntPtr.Zero);<br />
			result = ThemeAPI.DrawThemeBackground(pTHEME,pDC,9,1,ref rect,IntPtr.Zero);<br />
<br />
			clientDC.ReleaseHdc(pDC);<br />
			clientDC.Dispose();

What do you make of it?

Heath Stewart2-Apr-04 8:58

2-Apr-04 8:58

Deleting the HDC that way is fine if you don't use Graphics.GetHdc to get it. The reason is that the unmanaged pointer that the Graphics references needs to be freed, otherwise the Graphics object will complain about having an invalid handle when the Graphics.Dispose method tried to delete it.

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Heath Stewart1-Apr-04 8:46

1-Apr-04 8:46

You get that error when the application is not loaded into an STA (single-threaded apartment). Make sure you use the STAThreadAttribute on your entry point and that any controls in your library used in an application are created in the main thread.

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Tristan Rhodes1-Apr-04 10:39

1-Apr-04 10:39

Too late m8!

Got to that one on my own Smile | :)

MDIChild help

robmays1-Apr-04 8:37

robmays

1-Apr-04 8:37

there are lots of examples on how to set up child form from the MainMDI but i cant find anything on how to open a form from another child form and setting the MDIParent so as it becomes child form, where am i going wrong??? Cry | :((

Re: MDIChild help

Heath Stewart1-Apr-04 8:58

1-Apr-04 8:58

So long as you're not talking about an MDI child form within another MDI child form (which isn't supported in the .NET FCL), you can simply get the parent MDI form of the first child and add the new child as an MDI child of the parent:

MDIChildForm child = new MDIChildForm(); // Or whatever your class is
if (MdiParent != null)
  MdiParent.AddOwnedForm(child);

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Re: MDIChild help

robmays1-Apr-04 9:14

robmays

1-Apr-04 9:14

fantastic response and worked first time. Smile | :)

Give a panel a focus

Jonathan Slenders1-Apr-04 8:22

Jonathan Slenders

1-Apr-04 8:22

How can i make a panel that can receive a focus
I used the GotFocus and LostFocus events to turn the panel blue when focussed. But how can i set the CanReceiveFocus Property true so that you can use your keyboard (Tab and arrows) to give that control the focus. (That panel also conatains a picturebox and a label).

Thanks

Jonathan Slenders

Re: Give a panel a focus

Heath Stewart1-Apr-04 8:55

2 dimension textbox array

1-Apr-04 8:55

Extend the control and in your constructor call SetStyle(ControlStyles.Selectable, true).

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Re: Give a panel a focus

Jonathan Slenders5-Apr-04 7:50

Jonathan Slenders

5-Apr-04 7:50

Thank you very mush

hkl1-Apr-04 8:00

hkl

1-Apr-04 8:00

Hello,

May I know how I can create a 2 dimension textbox array? I know how to create a 1 dimension textbox array, but I am having trouble trying the 2D. Thank you!!

Re: 2 dimension textbox array

Heath Stewart1-Apr-04 8:53

Re: 2 dimension textbox array

1-Apr-04 8:53

It depends what kind of multi-dimensional array. There are multi-dimensional arrays and jagged arrays. The former is declared like this:

TextBox[,] boxes = new TextBox[,] {{textBox1, textBox1},
  {textBox1, textBox2}, {textBox2, textBox2}};

These types of arrays have fixed dimensions and sizes.

Jaggaed arrays' elements are arrays themselves, like this:

TextBox[][] boxes = new TextBox[] {
  new TextBox[] {textBox1, textBox1},
  new TextBox[] {textBox1, textBox2},
  new TextBox[] {textBox2, textBox2},
  new TextBox[] {textBox1},
  new TextBox[] {textBox2}};

As you can see, these can have different dimensions and sizes.

You can find more information by reading about Arrays[^] in the Visual C# language documentation.

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hkl1-Apr-04 9:30

hkl

1-Apr-04 9:30

Thank you

DragDrop registration failed - Error

Tristan Rhodes1-Apr-04 7:19

1-Apr-04 7:19

I've created a component Library, and i've built the P/Invoce commands into it to build a windows style component. However, when i try and run the following lines internaly from the component, or Externaly from the parent window, i get the "DragDrop registration failed."

<br />
			pTHEME = ThemeAPI.OpenThemeData(this.Handle,"Window");<br />
<br />
			IntPtr pDC = ThemeAPI.CreateCompatibleDC(IntPtr.Zero);<br />

I put a break point after these two lines, and they process ok for each window, producing pointers and executing successfuly. However, the program then skips to the end of the Main method, and throws the error.

Why is it doing this? I've read that it's a problem with Web Deployed Apps in .NET v1.0. But i have V1.1 and it's not a web app.

What can i do to solve it?

Cheers

Cata

Note: I have enabled windows styles as well, so that's not the problem.

leppie1-Apr-04 7:43

leppie

1-Apr-04 7:43

The Catalyst wrote:
IntPtr pDC = ThemeAPI.CreateCompatibleDC(IntPtr.Zero);

I dont know much of themes, but why are you passing a "NULL" pointer? Shouldnt you pass this.Handle instead?

^{top secret}

Tristan Rhodes1-Apr-04 9:34