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A General Fast Method Invoker

, 4 Jul 2006
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Method reflecting invoke is nice, but very frequently it can be too slow. This article describes an alternative method for dynamic method invoke.

Sample Image - FastMethodInvoker.gif


Sometimes, I run across the need to dynamically invoke the method of an object, where the actual method might not be known until run-time. Usually, Reflecting is nice, but frequently doing it can be too slow. This article describes an alternative method for dynamic method invocation.


When I read the article Fast Dynamic Property Accessors, I was thinking about my project, it has a lots of reflecting methods in circle. But it's methods not properties. But the DynamicMethod reminded me, maybe I could use Emit to generate a DynamicMethod to bind a special method before it can be invoked. I hope it will improve performance.

Using the Code

First, I reflected out the method which will be invoked:

MethodInfo methodInfo = typeof(Person).GetMethod("Say");

Then, I get the MethodInvoker to invoke:

FastInvokeHandler fastInvoker = GetMethodInvoker(methodInfo);
fastInvoker(new Person(), new object[]{"hello"});

Instead of using reflection method, invoke in the past:

methodInfo.Invoke(new Person(), new object[]{"hello"});


First, I need to define a delegate to adapt the dynamic method:

public delegate object FastInvokeHandler(object target, 
                                   object[] paramters);

It looks the same as the class MethodInfo's Invoke method. Yes, that means I can write the same code to use it like in the past.

This code generates the DynamicMethod:

public static FastInvokeHandler GetMethodInvoker(MethodInfo methodInfo)
    DynamicMethod dynamicMethod = new DynamicMethod(string.Empty, 
                     typeof(object), new Type[] { typeof(object), 
                     typeof(object[]) }, 
    ILGenerator il = dynamicMethod.GetILGenerator();
    ParameterInfo[] ps = methodInfo.GetParameters();
    Type[] paramTypes = new Type[ps.Length];
    for (int i = 0; i < paramTypes.Length; i++)
        paramTypes[i] = ps[i].ParameterType;
    LocalBuilder[] locals = new LocalBuilder[paramTypes.Length];
    for (int i = 0; i < paramTypes.Length; i++)
        locals[i] = il.DeclareLocal(paramTypes[i]);
    for (int i = 0; i < paramTypes.Length; i++)
        EmitFastInt(il, i);
        EmitCastToReference(il, paramTypes[i]);
        il.Emit(OpCodes.Stloc, locals[i]);
    for (int i = 0; i < paramTypes.Length; i++)
        il.Emit(OpCodes.Ldloc, locals[i]);
    il.EmitCall(OpCodes.Call, methodInfo, null);
    if (methodInfo.ReturnType == typeof(void))
        EmitBoxIfNeeded(il, methodInfo.ReturnType);
    FastInvokeHandler invoder = 
    return invoder;


Well, I think this is a general way that can be used instead of most of the reflection methods to get about 50 times performance improvement. Any suggestions for improvements are welcome.

Extra advantage (reminded by MaxGuernsey): If an exception occurs in your code, FastInovker would throw the original one, but the Method.Invoke would throw a TargetInvocationException.


  • 2006-7-05: Updated to add static method support. Thanks Manuel Abadia.
  • 2006-6-30: Updated to add ref/out parameter support. Thanks Roger for his nice suggestion.


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About the Author


China China
I am currently working for a .NET framework names AgileFramework. It's introduction at here:

Now I'm living in China. I have been designing and developing .NET based software applications for 5+ years.

Comments and Discussions

QuestionNot necessay at all PinmemberFatCatProgrammer22-Jan-13 9:25 
AnswerRe: Not necessay at all PinmemberLu Jing9-Jun-13 21:06 
AnswerRe: Not necessay at all Pinmembercajoncillos1-Jul-14 13:24 
GeneralRe: Not necessay at all PinmemberFatCatProgrammer1-Jul-14 17:10 
Questionabout your code's license Pinmemberqsmy12322-Aug-12 16:00 
QuestionLicense PinmemberSkeletor2323-Mar-12 6:05 
QuestionConstructorInfo Support. PinmemberMember 455125623-Jun-10 8:29 
AnswerRe: ConstructorInfo Support. PinmemberMember 455125623-Jun-10 10:00 
QuestionCan't work with 'struct' ? Pinmemberqmxle1-Oct-09 6:11 
GeneralExcellent! Accessibility fix possible. Pinmemberblack198122-Jul-09 3:49 
QuestionPartial Trust question PinmemberAndrey Belykh25-Apr-08 7:57 
Generalprivate member supported and easier way with better performance Pinmemberyzh_x1-Jul-07 20:38 
GeneralRe: private member supported and easier way with better performance PinmemberLinguar2-Jul-07 10:15 
GeneralRe: private member supported and easier way with better performance Pinmemberyzh_x2-Jul-07 17:44 
You are right, the signature is required to know.
But, there is small different, the method "say" can be assigned at runtime, not compile-time.

And this way has a fatal weakness, if the method is instance method and require to change the instance many times, this way will take much time.
the following Delegate method takes long time.
private extern bool BindToMethodInfo(object target, RuntimeMethodHandle method, RuntimeTypeHandle methodType, DelegateBindingFlags flags);
GeneralRe: private member supported and easier way with better performance PinmemberLinguar2-Jul-07 19:26 
GeneralWrapper PinmemberMick O'Neill7-Jun-07 14:46 
GeneralRe: Wrapper Pinmemberjohnnycrash9917-May-09 10:03 
GeneralComments and structure. PinmemberLinguar19-Mar-07 7:56 
GeneralRe: Comments and structure. PinmemberLuyan24-Mar-07 3:35 
GeneralA Wrapper class for your code Pinmemberbilly p6-Oct-06 10:35 
GeneralI think the result is not exact Pinmemberhappyhippyie3-Sep-06 1:10 
GeneralRe: I think the result is not exact Pinmemberueqt20071-Sep-07 20:42 
AnswerRe: I think the result is not exact Pinmemberxx91819-Jan-08 4:29 
QuestionMethodAccessException unhandled when using generic string types Pinmembercanerten9-Aug-06 3:20 
QuestionRe: MethodAccessException unhandled when using generic string types Pinmembercanerten9-Aug-06 3:47 

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