c# - Get OrderBy method using reflection -

i want implement generic pager , filter view model project , i'm stuck on getting orderby method using reflection. here i've tried, keep getting null methodinfo. seems i'm passing wrong type[] arguments getmethod() method, can't right.

    protected virtual expression<func<t, icomparable>> getorderbyexpression()     {         var type = typeof(t);         var property = type.getproperty("datasetname");         var parameter = expression.parameter(type, "x");         var propertyaccess = expression.makememberaccess(parameter, property);         var orderbyexp = expression.lambda(propertyaccess, parameter);         var methodinfo = typeof(enumerable).getmethod("orderby", new type[] { orderbyexp.body.type });         var predicatebody = expression.call(propertyaccess, methodinfo, orderbyexp);         var expression = expression.lambda<func<t, icomparable>>(predicatebody, parameter);          return expression;     } 

then enumerable.orderby extension method static method have use overload getmethod can specify bindingflags (bindingflags.static | bindingflags.public instead of default bindingflags.instance | bindingflags.public).

you have specify 2 parameters method - syntactically looks there 1 parameter because extension method there second parameter have specify.

this method want via reflection:

public static iorderedenumerable<tsource> orderby<tsource, tkey>(   ienumerable<tsource> source,   func<tsource, tkey> keyselector ) 

you need 2 parameter types:

var sourcetype = typeof(ienumerable<>).makegenerictype(type); var keyselectortype = orderbyexp.compile().gettype(); 

it seems way specific overload of method generic parameters have perform search. fortunately, there 2 overloads of enumerable.orderby , 1 want 1 2 parameters:

var genericmethodinfo = typeof(enumerable)   .getmethods(bindingflags.static | bindingflags.public)   .first(mi => mi.name == "orderby" && mi.getparameters().length == 2); var methodinfo = genericmethodinfo.makegenericmethod(sourcetype, keyselectortype); 

this returns desired methodinfo, have modify remaining 2 lines of code because method static method , have specify null instance in expression.call.