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Posted 27 Jun 2006


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A General Fast Method Invoker

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4.96/5 (75 votes)
4 Jul 20061 min read
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.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


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 Pin
FatCatProgrammer22-Jan-13 8:25
MemberFatCatProgrammer22-Jan-13 8:25 
AnswerRe: Not necessay at all Pin
Jingwood9-Jun-13 20:06
MemberJingwood9-Jun-13 20:06 
AnswerRe: Not necessay at all Pin
cajoncillos1-Jul-14 12:24
Membercajoncillos1-Jul-14 12:24 
GeneralRe: Not necessay at all Pin
FatCatProgrammer1-Jul-14 16:10
MemberFatCatProgrammer1-Jul-14 16:10 
Questionabout your code's license Pin
qsmy12322-Aug-12 15:00
Memberqsmy12322-Aug-12 15:00 
QuestionLicense Pin
Skeletor2323-Mar-12 5:05
MemberSkeletor2323-Mar-12 5:05 
QuestionConstructorInfo Support. Pin
Member 455125623-Jun-10 7:29
MemberMember 455125623-Jun-10 7:29 
AnswerRe: ConstructorInfo Support. Pin
Member 455125623-Jun-10 9:00
MemberMember 455125623-Jun-10 9:00 
QuestionCan't work with 'struct' ? Pin
qmxle1-Oct-09 5:11
Memberqmxle1-Oct-09 5:11 
GeneralExcellent! Accessibility fix possible. Pin
black198122-Jul-09 2:49
Memberblack198122-Jul-09 2:49 
QuestionPartial Trust question Pin
Andrey Belykh25-Apr-08 6:57
MemberAndrey Belykh25-Apr-08 6:57 
Generalprivate member supported and easier way with better performance Pin
yzh_x1-Jul-07 19:38
Memberyzh_x1-Jul-07 19:38 
GeneralRe: private member supported and easier way with better performance Pin
Linguar2-Jul-07 9:15
MemberLinguar2-Jul-07 9:15 
GeneralRe: private member supported and easier way with better performance Pin
yzh_x2-Jul-07 16:44
Memberyzh_x2-Jul-07 16:44 
GeneralRe: private member supported and easier way with better performance Pin
Linguar2-Jul-07 18:26
MemberLinguar2-Jul-07 18:26 
GeneralWrapper Pin
Midi_Mick7-Jun-07 13:46
professionalMidi_Mick7-Jun-07 13:46 
GeneralRe: Wrapper Pin
johnnycrash9917-May-09 9:03
Memberjohnnycrash9917-May-09 9:03 
GeneralComments and structure. Pin
Linguar19-Mar-07 6:56
MemberLinguar19-Mar-07 6:56 
GeneralRe: Comments and structure. Pin
Luyan24-Mar-07 2:35
MemberLuyan24-Mar-07 2:35 
GeneralA Wrapper class for your code Pin
billy p6-Oct-06 9:35
Memberbilly p6-Oct-06 9:35 
Hi Luyan,

Thanks much for your project. It was extremely helpful in some development work that I have recently done. I decided that I would send you a little wrapper class, and a test project that I did using your code. I couldn't quite find an email address for you, so I posted it on code project (FastInvokeWrapper.asp).

Of course, I botched up the links, so it's going to take a few days before it get's properly posted. Anyway, thanks again for your project.

Billy p.

GeneralI think the result is not exact Pin
happyhippyie3-Sep-06 0:10
Memberhappyhippyie3-Sep-06 0:10 
GeneralRe: I think the result is not exact Pin
ueqt20071-Sep-07 19:42
Memberueqt20071-Sep-07 19:42 
AnswerRe: I think the result is not exact Pin
xx91819-Jan-08 3:29
Memberxx91819-Jan-08 3:29 
QuestionMethodAccessException unhandled when using generic string types Pin
Can Erten9-Aug-06 2:20
MemberCan Erten9-Aug-06 2:20 
QuestionRe: MethodAccessException unhandled when using generic string types Pin
Can Erten9-Aug-06 2:47
MemberCan Erten9-Aug-06 2:47 

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