I wish to generate (emit) class that implement an Interface at run-time with C#.
I have succeeded to emit methods and properties, but I failed to emit an event.
Here is the code I wish to emit:
Namespace: TestInterfaces, Class: TestIImplementMe.
public event EventHandler SimpleEvent;
Here is the IL code generated:
.event [mscorlib]System.EventHandler SimpleEvent
{
.addon instance void TestInterfaces.TestIImplementMe::add_SimpleEvent(class [mscorlib]System.EventHandler)
.removeon instance void TestInterfaces.TestIImplementMe::remove_SimpleEvent(class [mscorlib]System.EventHandler)
}
.method public final hidebysig specialname newslot virtual
instance void add_SimpleEvent (
class [mscorlib]System.EventHandler 'value'
) cil managed
{
// Method begins at RVA 0x330c
// Code size 48 (0x30)
.maxstack 3
.locals init (
[0] class [mscorlib]System.EventHandler,
[1] class [mscorlib]System.EventHandler,
[2] class [mscorlib]System.EventHandler,
[3] bool
)
IL_0000: ldarg.0
IL_0001: ldfld class [mscorlib]System.EventHandler TestInterfaces.TestIImplementMe::SimpleEvent
IL_0006: stloc.0
// loop start (head: IL_0007)
IL_0007: ldloc.0
IL_0008: stloc.1
IL_0009: ldloc.1
IL_000a: ldarg.1
IL_000b: call class [mscorlib]System.Delegate [mscorlib]System.Delegate::Combine(class [mscorlib]System.Delegate, class [mscorlib]System.Delegate)
IL_0010: castclass [mscorlib]System.EventHandler
IL_0015: stloc.2
IL_0016: ldarg.0
IL_0017: ldflda class [mscorlib]System.EventHandler TestInterfaces.TestIImplementMe::SimpleEvent
IL_001c: ldloc.2
IL_001d: ldloc.1
IL_001e: call !!0 [mscorlib]System.Threading.Interlocked::CompareExchange<class [mscorlib]System.EventHandler>(!!0&, !!0, !!0)
IL_0023: stloc.0
IL_0024: ldloc.0
IL_0025: ldloc.1
IL_0026: ceq
IL_0028: ldc.i4.0
IL_0029: ceq
IL_002b: stloc.3
IL_002c: ldloc.3
IL_002d: brtrue.s IL_0007
// end loop
IL_002f: ret
} // end of method TestIImplementMe::add_SimpleEvent
.method public final hidebysig specialname newslot virtual
instance void remove_SimpleEvent (
class [mscorlib]System.EventHandler 'value'
) cil managed
{
// Method begins at RVA 0x3348
// Code size 48 (0x30)
.maxstack 3
.locals init (
[0] class [mscorlib]System.EventHandler,
[1] class [mscorlib]System.EventHandler,
[2] class [mscorlib]System.EventHandler,
[3] bool
)
IL_0000: ldarg.0
IL_0001: ldfld class [mscorlib]System.EventHandler TestInterfaces.TestIImplementMe::SimpleEvent
IL_0006: stloc.0
// loop start (head: IL_0007)
IL_0007: ldloc.0
IL_0008: stloc.1
IL_0009: ldloc.1
IL_000a: ldarg.1
IL_000b: call class [mscorlib]System.Delegate [mscorlib]System.Delegate::Remove(class [mscorlib]System.Delegate, class [mscorlib]System.Delegate)
IL_0010: castclass [mscorlib]System.EventHandler
IL_0015: stloc.2
IL_0016: ldarg.0
IL_0017: ldflda class [mscorlib]System.EventHandler TestInterfaces.TestIImplementMe::SimpleEvent
IL_001c: ldloc.2
IL_001d: ldloc.1
IL_001e: call !!0 [mscorlib]System.Threading.Interlocked::CompareExchange<class [mscorlib]System.EventHandler>(!!0&, !!0, !!0)
IL_0023: stloc.0
IL_0024: ldloc.0
IL_0025: ldloc.1
IL_0026: ceq
IL_0028: ldc.i4.0
IL_0029: ceq
IL_002b: stloc.3
IL_002c: ldloc.3
IL_002d: brtrue.s IL_0007
// end loop
IL_002f: ret
} // end of method TestIImplementMe::remove_SimpleEvent
I managed to do all but this line: IL_001e: call !!0 [mscorlib]System.Threading.Interlocked::CompareExchange(!!0&, !!0, !!0)
What is the meaning of: !!0, !!0&?
How do I call this method with IL emit?
I tried to call the method, but when I add handler:
obj.SimpleEvent += new EventHandler(obj_SimpleEvent);
I get this exception:
System.BadImageFormatException was unhandled
Message=An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)
Source=DataBuilderAssembly
StackTrace:
at NewTest.add_SimpleEvent(EventHandler value)
at TestInterfaces.Program.Main(String[] args) in D:\Dev\Private\TestInterfaces\TestInterfaces\Program.cs:line 47
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
Here is the code to emit event's add method where
methodName = "add_SimpleEvent";
actionHanler = typeof(Delegate).GetMethod("Combine", new Type[]{typeof(Delegate),typeof(Delegate)});
eventField = typeBuilder.DefineField(info.Name, info.EventHandlerType, FieldAttributes.Private);
compareExchange = GetGenericMethod(typeof(Interlocked), "CompareExchange");// finds the correct method to call.
// thanks to @marc, create the specific method with the correct type
compareExchange = compareExchange.MakeGenericMethod(info.EventHandlerType);
GenerateEventMethod
private static MethodBuilder GenerateEventMethod(string methodName, MethodInfo actionHanler, TypeBuilder typeBuilder, EventInfo info, FieldBuilder eventField, MethodInfo compareExchange)
{
MethodBuilder method = typeBuilder.DefineMethod(methodName, InternalMethodsAttributes, null, new Type[] { info.EventHandlerType });
method.DefineParameter(0, ParameterAttributes.Retval, null);
method.DefineParameter(1, ParameterAttributes.In, "value");
ILGenerator il = method.GetILGenerator();
il.DeclareLocal(info.EventHandlerType);
il.DeclareLocal(info.EventHandlerType);
il.DeclareLocal(info.EventHandlerType);
il.DeclareLocal(typeof (bool));
Label loop = il.DefineLabel();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldfld, eventField);
il.Emit(OpCodes.Stloc_0);
il.MarkLabel(loop);// loop start (head: IL_0007)
il.Emit(OpCodes.Ldloc_0);
il.Emit(OpCodes.Stloc_1);
il.Emit(OpCodes.Ldloc_1);
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Call, actionHanler);
il.Emit(OpCodes.Castclass, info.EventHandlerType);
il.Emit(OpCodes.Stloc_2);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldflda, eventField);
il.Emit(OpCodes.Ldloc_2);
il.Emit(OpCodes.Ldloc_1);
// How to do this?
//IL_001e: call !!0 [mscorlib]System.Threading.Interlocked::CompareExchange<class [mscorlib]System.EventHandler`1<class [mscorlib]System.ConsoleCancelEventArgs>>(!!0&, !!0, !!0)
//il.Emit(OpCodes.Call, !!0 compareExchange(!!0&,!!0, !!0));
il.Emit(OpCodes.Call, compareExchange);
il.Emit(OpCodes.Stloc_0);
il.Emit(OpCodes.Ldloc_0);
il.Emit(OpCodes.Ldloc_1);
il.Emit(OpCodes.Ceq);
il.Emit(OpCodes.Ldc_I4_0);
il.Emit(OpCodes.Ceq);
il.Emit(OpCodes.Stloc_3);
il.Emit(OpCodes.Ldloc_3);
il.Emit(OpCodes.Brtrue_S, loop);
// end loop
il.Emit(OpCodes.Ret);
return method;
}
GetGenericMethod (specific for this issue):
private static MethodInfo GetGenericMethod(Type type, string methodName)
{
var q = from m in type.GetMethods()
where m.Name == methodName && m.IsGenericMethod
select m;
return q.FirstOrDefault();
}
Thanks, Ofir
!!0 is the T in CompareExchange<T> (i.e. !!0 is the first (zero-based) generic type parameter), and !!0& is ref T - but all of this is just specifying the overload. The important bit is the ldflda (loads by-ref the field), ldloc.2 and ldloc.1 in the lines before that, and the fact that it returns a T.