hi Mattias,

Thank you for your response.  I tried to use various forms of the "c-style" array, however I was able to verify in the debugger that the CLR marshaller is copying the data array, (probably twice, once for in, and once for out).  This performance is not satisfactory for my application.

This isn't an uncommon requirement, so I wonder what solution the dotnet team had in mind.

This is the only technique I've found to work so far without any copying:

<<COM function>>
HRESULT GetImagePixels([in] LONG bytes); //receives a pointer to where it should load the pixels

<<managed code>>

byte[] rgbdata = new byte[numBytes];

//Pin the array so it can't be moved
GCHandle pinHandle = GCHandle.Alloc(rgbdata,GCHandleType.Pinned);
try
{
//Grab pointer to element zero, as an int
IntPtr ptr = Marshal.UnsafeAddrOfPinnedArrayElement(rgbdata,0);
 int ptrAsInt = ptr.ToInt32();
 //Load the pixels from unmanaged COM
 rdr.GetImagePixels(ptrAsInt);
}
catch{throw;}
finally{pinHandle.Free();}