Question

I want to do this:

MethodInfo m = myList.GetType().GetMethod('ConvertAll', System.Reflection.BindingFlags.InvokeMethod).MakeGenericMethod(typeof(object)); List<object> myConvertedList = (List<object>)m.Invoke(myList, new object[]{ (t => (object)t)}); 

myList is a generic list of a specific type (unknown to the application), and I want to convert it to a list of objects to do some operations.

However this fails with this error: ‘Cannot convert lambda expression to type ‘object’ because it is not a delegate type’

Can you help me find what’s wrong? Am I trying to do something that’s not possible?

Is there some other way to achieve the same thing?

Answer 1

A lambda expression is convertible to either a delegate type or an expression tree with the right signature – but you need to specify which delegate type it is.

I think your code would be much simpler if you made this a generic method:

public static List<object> ConvertToListOfObjects<T>(List<T> list) {     return list.ConvertAll<object>(t => t); } 

Then you just need to find and invoke that method generically:

MethodInfo method = typeof(Foo).GetMethod('ConvertToListOfObjects',     BindingFlags.Static | BindingFlags.Public); Type listType = list.GetType().GetGenericArguments()[0]; MethodInfo concrete = method.MakeGenericMethod(new [] { listType }); List<object> objectList = (List<object>) concrete.Invoke(null,                                                     new object[]{list}); 

Complete example:

using System; using System.Reflection; using System.Collections.Generic;  class Test {     public static List<object> ConvertToListOfObjects<T>(List<T> list)     {         return list.ConvertAll<object>(t => t);     }      static void Main()     {         object list = new List<int> { 1, 2, 3, 4 };          MethodInfo method = typeof(Test).GetMethod('ConvertToListOfObjects',             BindingFlags.Static | BindingFlags.Public);         Type listType = list.GetType().GetGenericArguments()[0];         MethodInfo concrete = method.MakeGenericMethod(new [] { listType });         List<object> objectList = (List<object>) concrete.Invoke(null,                                                     new object[] {list});          foreach (object o in objectList)         {             Console.WriteLine(o);         }     } }