private System.Drawing.Bitmap BitmapFromSource(BitmapSource bitmapsource)
 {
     System.Drawing.Bitmap bitmap;
     using (MemoryStream outStream = new MemoryStream())
     {
       BitmapEncoder enc = new BmpBitmapEncoder();

       enc.Frames.Add(BitmapFrame.Create(bitmapsource));
       enc.Save(outStream);
       bitmap = new System.Drawing.Bitmap(outStream);
     }
     return bitmap;
 }

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Converting BitmapSource to Bitmap in C#

How to convert BitmapSource to Bitmap

c#

C#