c# - Select Right Generic Method with Reflection -


i want select right generic method via reflection , call it.

usually quite easy. example

var method = typeof(mytype).getmethod("themethod"); var typedmethod = method.makegenericmethod(thetypetoinstantiate);

however issue start when there different generic overloads of method. example static-methods in system.linq.queryable-class. there 2 definitions of 'where'-method

static iqueryable<t> where(this iqueryable<t> source, expression<func<t,bool>> predicate) static iqueryable<t> where(this iqueryable<t> source, expression<func<t,int,bool>> predicate)

this meand getmethod doesn't work, because cannot destiguish two. therefore want select right one.

so far took first or second method, depending on need. this:

var method = typeof (queryable).getmethods().first(m => m.name == "where"); var typedmethod = method.makegenericmethod(thetypetoinstantiate);

however i'm not happy this, because make huge assumption first method right one. rather want find right method argument type. couldn't figure out how.

i tried passing 'types', didn't work.

        var method = typeof (queryable).getmethod(             "where", bindingflags.static,             null,             new type[] {typeof (iqueryable<t>), typeof (expression<func<t, bool>>)},             null);

so has idea how can find 'right' generic method via reflection. example right version of 'where'-method on queryable-class?

it can done, it's not pretty!

for example, first overload of where mentioned in question this:

var where1 = typeof(queryable).getmethods()                  .where(x => x.name == "where")                  .select(x => new { m = x, p = x.getparameters() })                  .where(x => x.p.length == 2                              && x.p[0].parametertype.isgenerictype                              && x.p[0].parametertype.getgenerictypedefinition() == typeof(iqueryable<>)                              && x.p[1].parametertype.isgenerictype                              && x.p[1].parametertype.getgenerictypedefinition() == typeof(expression<>))                  .select(x => new { x.m, = x.p[1].parametertype.getgenericarguments() })                  .where(x => x.a[0].isgenerictype                              && x.a[0].getgenerictypedefinition() == typeof(func<,>))                  .select(x => new { x.m, = x.a[0].getgenericarguments() })                  .where(x => x.a[0].isgenericparameter                              && x.a[1] == typeof(bool))                  .select(x => x.m)                  .singleordefault();

or if wanted second overload:

var where2 = typeof(queryable).getmethods()                  .where(x => x.name == "where")                  .select(x => new { m = x, p = x.getparameters() })                  .where(x => x.p.length == 2                              && x.p[0].parametertype.isgenerictype                              && x.p[0].parametertype.getgenerictypedefinition() == typeof(iqueryable<>)                              && x.p[1].parametertype.isgenerictype                              && x.p[1].parametertype.getgenerictypedefinition() == typeof(expression<>))                  .select(x => new { x.m, = x.p[1].parametertype.getgenericarguments() })                  .where(x => x.a[0].isgenerictype                              && x.a[0].getgenerictypedefinition() == typeof(func<,,>))                  .select(x => new { x.m, = x.a[0].getgenericarguments() })                  .where(x => x.a[0].isgenericparameter                              && x.a[1] == typeof(int)                              && x.a[2] == typeof(bool))                  .select(x => x.m)                  .singleordefault();

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