Invoking a virtual method non-virtually

funny wallpaper » Invoking a virtual method non-virtually

funny wallpaper » Invoking a virtual method non-virtually — Sun, 17 Aug 2008 02:32:05 GMT

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re: Invoking a virtual method non-virtually

atykhyy — Sat, 23 Aug 2008 12:07:47 GMT

I was investigating non-virtual calls the other day, because DynamicILGenerator overrides some ILGenerator's methods with functions throwing NotSupportedExceptions for no reason I could discover and I had to call them. At first I developed a solution with dynamic methods, very similar to what you propose here, but actually there *is* a way do do it with delegates. The relevant code looks like this:

private delegate void BeginFaultBlock () ;

private readonly static ConstructorInfo dBeginFaultBlock = typeof (BeginFilterBlock).GetConstructors () [0] ;

private readonly static IntPtr iBeginFaultBlock = typeof (ILGenerator).GetMethod ("BeginFaultBlock") .MethodHandle.GetFunctionPointer () ;

public static BeginFaultBlock MakeBeginFaultBlockDelegate (ILGenerator generator)

{

return (BeginFaultBlock) dBeginFaultBlock.Invoke (new object[] { generator, iBeginFaultBlock })) () ;

}

I couldn't get invocation through delegates to work reliably when the delegate receives the generator as an argument, i.e.

private delegate void BeginFaultBlock (ILGenerator generator) ; // no good

but maybe UnboundDelegate can handle this.

re: Invoking a virtual method non-virtually

rmbyers — Tue, 26 Aug 2008 08:40:14 GMT

Interesting. I didn't realize you could create a delegate with an explicit method address like that - thanks! I'm not sure if there are any gotchas associated with the use of RuntimeMethodHandle.GetFunctionPointer, etc.

Of course, using a trick like this to get around the fact that DynamicILGenerator doesn't support some opporations is almost certainly asking for trouble (at the very least, it might break in a future version or service pack of the runtime, since it's not verifiable to make a call circumventing virtual dispatch like this).