GDI+ Drawing in C# application

[Espen]

Hi

I have a C# application that should display a chart, the chart drawing
is done by a COM object. I have tried to use dllimport with gdi32.dll
and created compatibleDC and compatibleBitmap with the hdc from the
graphics object. The COM object is trying to draw on the compatibleDC
and I try to create a bitmap from the hdc when the c++ drawing is
finished. The image is not displaying anything, it is just black.

How is it possible to display a bitmap created from a hdc in a c#
application when the drawing is done from a C++ COM object?

Here is my sample code:

IntPtr hDC = this.CreateGraphics().GetHdc();
IntPtr hMemDC = CreateCompatibleDC(hDC); //Call gdi32.dll
IntPtr hBitmap = CreateCompatibleBitmap(hDC);//Call gdi32.dll
SelectObject(hMemDC,hBitmap);//Call gdi32.dll
DrawChart(hMemDC);//The chart drawing done by the COM object
Bitmap bmp = System.Drawing.Image.FromHbitmap(hBitmap);
pictureBox1.Image = bmp;

Can anybody please tell me what I'm doing wrong?

Thanks!

Espen

 

[Dmytro Lapshyn [MVP]]

Hi,

What if you just create a System.Drawing.Bitmap class with an appropriate
pixel format, then create a Graphics instance with the static
Graphics.FromImage method and then use the GetHdc() method on the created
Graphics instance to pass the HDC to the COM object?

 

[Espen]

Hi

Thanks for the reply.

I tried your suggestion but the result was the same, the image is just
blue. My drawrect from the COM component is not showing.

Espen