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I am creating a Bitmap object and from that Bitmap object creating an Icon and then Disposing them accordingly. While running the code I collected GDI object count after each GDI operation. Observed that after calling Dispose on the Bitmap object, GDI object count is still same.

class Icon_ResouceLeak
     static void Main(string[] args)
         // the program starts with 18 GDI objects..

         var bmp = new Bitmap("imagePath");
         // 25 GDI objects..

         IntPtr ptr = bmp.GetHicon();
         // 30 GDI Objects..

         Icon newIcon = Icon.FromHandle(ptr);

         var clonedIcon = (Icon)newIcon.Clone();
         // 33 GDI objects..

         // 30 GDI objects ..

         // 27 GDI objects ..

         // 27 GDI objects..

         // still 27 GDI objects? 

     [DllImport("user32.dll", CharSet = CharSet.Auto)]
     extern static bool DestroyIcon(IntPtr handle);

What I have tried:

bmp.Dispose() calls Image.Dispsoe(). Which internally calls, SafeNativeMethods.Gdip.GdipDisposeImage(new HandleRef(this, nativeImage));
if this is the case then why it is not released.
Updated 3 days ago

1 solution

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Solution 1

Member 11799596 3 days ago
I understand that after Icon.FromHandle, the field ownHandle is false, and thus Dispose from FromHandle won't call DestroyIcon. So both DetroyIcon and Dispose needs to be called.

Here my doubt is different. Why after calling bmp.Dispose() the GDI count is not getting reduced.
RickZeeland 3 days ago
If you are calling from C# it may have to do with the Garbage Collector, this can take some time before cleanup.
Member 11799596 3 days ago
With Dispose do we need to still wait for GC. I am bit confused on this.
Even if you see the Dispose implementation of Image, it calls SafeNativeMethods.Gdip.GdipDisposeImage(new HandleRef(this, nativeImage)) and then SuppressFinalize.
RickZeeland 3 days ago
System.GC.Collect() forces the garbage collector to run, but this is not advised by Microsoft.

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