How do I detect that an object is a generic collection, and what types it contains?

Question

I have a string serialization utility that takes a variable of (almost) any type and converts it into a string. Thus, for example, according to my convention, an integer va

Answer 1

Re your conundrum; I'm assuming stringifyList is a generic method? You would need to invoke it with reflection:

MethodInfo method = typeof(SomeType).GetMethod("stringifyList")
            .MakeGenericMethod(lt).Invoke({target}, new object[] {o});

where {target} is null for a static method, or this for an instance method on the current instance.

Further - I wouldn't assume that all collections are a: based on List, b: generic types. The important thing is: do they implement IList for some T?

Here's a complete example:

using System;
using System.Collections.Generic;
static class Program {
    static Type GetListType(Type type) {
        foreach (Type intType in type.GetInterfaces()) {
            if (intType.IsGenericType
                && intType.GetGenericTypeDefinition() == typeof(IList<>)) {
                return intType.GetGenericArguments()[0];
            }
        }
        return null;
    }
    static void Main() {
        object o = new List { 1, 2, 3, 4, 5 };
        Type t = o.GetType();
        Type lt = GetListType(t);
        if (lt != null) {
            typeof(Program).GetMethod("StringifyList")
                .MakeGenericMethod(lt).Invoke(null,
                new object[] { o });
        }
    }
    public static void StringifyList(IList list) {
        Console.WriteLine("Working with " + typeof(T).Name);
    }
}