c# delegate instance 被回收

MIL 的process 範例中有這一段
            MIL_DIG_HOOK_FUNCTION_PTR ProcessingFunctionPtr = new MIL_DIG_HOOK_FUNCTION_PTR(ProcessingFunction);

            MIL.MdigProcess(MilDigitizer, MilGrabBufferList, MilGrabBufferListSize, MIL.M_START, MIL.M_DEFAULT, ProcessingFunctionPtr, GCHandle.ToIntPtr(hUserData));

其中

public delegate MIL_INT MIL_DIG_HOOK_FUNCTION_PTR(MIL_INT HookType, MIL_ID EventId, IntPtr UserDataPtr);

但如果是用在winform 應用程式裡面,如果把上面那段放在Form的Initial中，需要把 ProcessingFunctionPtr 定義成在 Form的Class底下的static member

MyForm:Form

{

static   MIL_DIG_HOOK_FUNCTION_PTR ProcessingFunctionPtr;

void MyForm()

{

  ...

 ProcessingFunctionPtr = new MIL_DIG_HOOK_FUNCTION_PTR(ProcessingFunction);

            MIL.MdigProcess(MilDigitizer, MilGrabBufferList, MilGrabBufferListSize, MIL.M_START, MIL.M_DEFAULT, ProcessingFunctionPtr, GCHandle.ToIntPtr(hUserData));

}

}

否則在執行期ProcessingFunctionPtr會被Gabage collection清掉而產生error 

但在C# 2.0 好像可以直接寫成

 ProcessingFunctionPtr = ProcessingFunction;