c# - How to use reflection to get extension method on generic type -

from various sources on teh interwebs i've gleaned following function:

public static nullable<t> tryparsenullable<t>(this nullable<t> t, string input) t : struct {     if (string.isnullorempty(input))         return default(t);      nullable<t> result = new nullable<t>();     try     {         iconvertible convertiblestring = (iconvertible)input;         result = new nullable<t>((t)convertiblestring.totype(typeof(t), cultureinfo.currentculture));     }     catch (invalidcastexception) { }     catch (formatexception) { }      return result; } 

i've made extension method, , works fine if call directly:

int? input = new int?().tryparsenullable("12345"); 

my problem occurs when try call using reflection within context of generic function. full of answers describing how methodinfo of generic methods , static methods, can't seem put these in right way.
i've correctly determined passed generic type generic type (nullable<>), want use reflection call tryparsenullable extension method on nullable<>:

public static t getvalue<t>(string name, t defaultvalue) {     string result = getsomestringvalue(name);     if (string.isnullorempty(result)) return defaultvalue;      try     {         if (typeof(t).isgenerictype && typeof(t).getgenerictypedefinition() == typeof(nullable<>))         {             methodinfo methodinfo;              //using tryparse() of underlying type works isn't way want             //-------------------------------------------------------------------------------------------              nullableconverter nc = new nullableconverter(typeof(t));             type t = nc.underlyingtype;              methodinfo = t.getmethod("tryparse", bindingflags.public | bindingflags.static, type.defaultbinder, new[] { typeof(string), t.makebyreftype() }, null);             if (methodinfo != null)             {                 var inputparameters = new object[] { result, null };                 methodinfo.invoke(null, inputparameters);                 return (t) inputparameters[1];             }              //start of problem area             //-------------------------              type ttype = typeof(t);              //this works undesirable (due reference class containing static method):             methodinfo = typeof(parentextensionsclass).getmethod("tryparsenullable", bindingflags.public | bindingflags.static);             if (methodinfo != null)                 console.writeline(methodinfo);              //standard way of getting static method, doesn't work (getmethod() returns null):             methodinfo = ttype.getmethod("tryparsenullable", bindingflags.public | bindingflags.static);             if (methodinfo != null)                 console.writeline(methodinfo);              //jon skeet's advised method, doesn't work in case (again getmethod() returns null):             //(see footnote link answer)             methodinfo = ttype.getmethod("tryparsenullable");             methodinfo = methodinfo.makegenericmethod(ttype);             if (methodinfo != null)                 console.writeline(methodinfo);              //another random attempt (also doesn't work):             methodinfo = ttype.getmethod("tryparsenullable", bindingflags.public | bindingflags.static, type.defaultbinder, new[] { typeof(string) }, null);             if (methodinfo != null)                 console.writeline(methodinfo);         }          // if far, not handling type yet         throw new argumentexception("the type " + defaultvalue.gettype() + " not yet supported getvalue<t>.", "t");     }     catch (exception e)     {         [snip]     } } 

can put me out of misery?
typeof(t) returns correct type info, figure maybe i'm using little incorrectly getmethod() call, or haven't specified right parameters call getmethod().

_{1. link referenced jon skeet answer}

the problem extension methods don't modify type 'extending'. happens behind scenes compiler transparently translates calls seem made on object in question calls static method.

ie.

int? input = new int?().tryparsenullable("12345"); // becomes... int? input = yourclass.tryparsenullable(new int?(), "12345"); 

from there becomes obvious why it's not showing via reflection. explains why have have using directive namespace yourclass defined extension methods visible compiler. how can @ information, i'm not sure there way, short of running on declared types (perhaps filtered list of interesting classes, if know sort of information @ compile time) looking static methods extensionmethodattribute ([extensionmethod]) defined on them, trying parse methodinfo parameter list work out if work on nullable<>.