Thinking Inside a Different Box

   //free the memory
   Free( MemoryPtr );

   // Check if Left is less than Right
   if( Window.Left < Window.Right )
   {
      // move to the left
      MoveLeft();
   }
   // create the directory
   Directory.Create( "homedir" );
   // open the file
   Stream file = FileStream.Open( "homedir\\hijohn.txt" );
   // close the file
   file.Close();

public struct StructLand
{
    public int val1, val2;
}

public class Woombey
{
    [DllImport( "woombey.dll" )]
    public static extern void DoSomething( ref StructLand woot );
}

public class Invoker
{
    public void Method()
    {
        StructLand woot = new StructLand();
        Woombey.DoSomething( woot );
    }
}

public class Woombey
{
    [DllImport( "woombey.dll" )]
    public static extern void DoSomething( IntPtr woot );
}

public class Invoker
{
    public void Method()
    {
        StructLand woot = new StructLand();
        unsafe fixed( Structland *wootptr = &woot )
		{
        	Woombey.DoSomething( new IntPtr( wootptr ) );
		}
    }
}

public class Woombey
{
    [DllImport( "woombey.dll" )]
    public static extern void DoSomething( Point point );

    [DllImport( "woombey.dll" )]
    public static extern void DoSomething( int xloc, int yloc );
}

public class Woombey
{
    [DllImport( "woombey.dll" )]
    public static extern void DoSomething( int xloc, int yloc );

    [DllImport( "woombey.dll" )]
    public static void DoSomething( Point point )
    {
        DoSomething( point.X, point.Y );
    }
}

public class Woombey
{
    [DllImport( "woombey.dll" )]
    public static extern void DoSomething( ref StructLand woot );

    [DllImport( "woombey.dll" )]
    public static extern void DoSomething( int pointer );
}

public class Invoker
{
    public void Method()
    {
        StructLand woot = new StructLand();
        unsafe fixed( Structland *wootptr = &woot )
		{
        	Woombey.DoSomething( (int)wootptr );
            // ... or you could do this:
        	Woombey.DoSomething( new IntPtr( wootptr ).ToInt32() );
		}
    }
}

public class Woombey
{
    [DllImport( "woombey.dll" )]
    public static unsafe extern void DoSomething( StructLand* woot );
}

public class Invoker
{
    public void Method()
    {
        StructLand woot = new StructLand();
        unsafe fixed( Structland *wootptr = &woot )
		{
        	Woombey.DoSomething( wootptr );
		}
    }
}

public class Joe
{
	[UnmanagedFunctionPointer( CallingConvention.Cdecl )]
	public delegate void UnmanagedPointerThingie( IntPtr handle, int param_a, int param_b );
	
	[DllImport( "woot.dll" )]
	static extern void ManagedEntryPoint( ref UnmanagedDataSet data );
	
	[StructLayout( LayoutKind.Sequential )]
	static struct UnmanagedDataSet
	{
		public IntPtr ActionPtrA;
		public IntPtr ActionPtrB;
	}

	public UnmanagedPointerThingie ActionA;
	public UnmanagedPointerThingie ActionB;
	
	public void InitStuff()
	{
		UnmanagedDataSet data = new UnmanagedDataSet();
		ManagedEntryPoint( ref data );
		
		// Create delegates out of the function pointer here:
		ActionA = (UnmanagedPointerThingie)Marshal.GetDelegateForFunctionPointer(
			data.ActionPtrA, typeof( UnmanagedPointerThingie ) );
		ActionB = (UnmanagedPointerThingie)Marshal.GetDelegateForFunctionPointer(
			data.ActionPtrB, typeof( UnmanagedPointerThingie ) );
			
		// And now we Invoke this bad boy:
		ActionA( handle, param, param );
	}	
}

__declspec( dllexport ) void _stdcall MyDLL_ActionInvoke( void (_cdecl *action)( void *, int, int ),
	void *handle, int param1, int param2 )
{
	action( handle, param1, param2 );
}

public class Joe
{
	[StructLayout( LayoutKind.Sequential )]
	static struct UnmanagedDataSet
	{
		public IntPtr ActionPtrA;
		public IntPtr ActionPtrB;
	}

	[DllImport( "woot.dll" )]
	static extern void ManagedEntryPoint( ref UnmanagedDataSet data );

	[DllImport( "allmine.dll" )]
	static extern void MyDLL_ActionInvoke( IntPtr func, IntPtr handle, int param1, int param2 );
	
	public void InitStuff()
	{
		UnmanagedDataSet data = new UnmanagedDataSet();
		ManagedEntryPoint( ref data );

		// Now to invoke this bad boy, the Fast Way(tm)
		MyDLL_ActionInvoke( data.ActionPtrA, handle, param, param );
	}
}