Get a generic method without using GetMethods

Solved (by hacking LINQ)!

I saw your question while researching the same problem. After finding no good solution, I had the idea to look at the LINQ expression tree. Here’s what I came up with:

public static MethodInfo GetOrderByMethod<TElement, TSortKey>()
{
    Func<TElement, TSortKey> fakeKeySelector = element => default(TSortKey);

    Expression<Func<IEnumerable<TElement>, IOrderedEnumerable<TElement>>> lamda
        = list => list.OrderBy(fakeKeySelector);

    return (lamda.Body as MethodCallExpression).Method;
}

static void Main(string[] args)
{
    List<int> ints = new List<int>() { 9, 10, 3 };
    MethodInfo mi = GetOrderByMethod<int, string>();           
    Func<int,string> keySelector = i => i.ToString();
    IEnumerable<int> sortedList = mi.Invoke(null, new object[] { ints, 
                                                                 keySelector }
                                           ) as IEnumerable<int>;

    foreach (int i in sortedList)
    {
        Console.WriteLine(i);
    }
}

output: 10 3 9

EDIT: Here is how to get the method if you don’t know the type at compile-time:

public static MethodInfo GetOrderByMethod(Type elementType, Type sortKeyType)
{
    MethodInfo mi = typeof(Program).GetMethod("GetOrderByMethod", Type.EmptyTypes);

    var getOrderByMethod = mi.MakeGenericMethod(new Type[] { elementType,
                                                             sortKeyType });
    return getOrderByMethod.Invoke(null, new object[] { }) as MethodInfo;
}

Be sure to replace typeof(Program) with typeof(WhateverClassYouDeclareTheseMethodsIn).