Assembly.GetType("[...]", true); throws TypeLoadException

Question

My code:

//App, Core.cs
using System;
using System.IO;
using System.Reflection;

namespace Game
{
    public static void Main(string[] args)
    {
        Assembly a = Assembly.LoadFile(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "mods\\ExampleMod.dll"));
        var x1 = a.GetType("PTF_Mod.Mod_Main");
        var x2 = x1.GetMethod("OnStart");
        var x3 = x2.Invoke(null, new object[] { });

        while(true);
    }
}


//App, ModCrew.cs
using System;
using System.Reflection;

namespace Engine
{
    public static class ModCrew
    {
        public class Mod
        {
            public void ItWorks()
            {
                Console.WriteLine("It works!");
            }
        }
    }
}

//DLL, Mod_Main.cs
using System;
using System.Reflection;

namespace PTF_Mod
{
    public static class Mod_Main
    {
        public static void OnStart()
        {
            var exe = Assembly.GetCallingAssembly();
            Console.WriteLine(exe.Location); //Location is valid
            var x = exe.GetType("Engine.ModCrew.Mod", true); //But here I get exception
            var y = Activator.CreateInstance(x);

            x.GetMethod("ItWorks", BindingFlags.Instance).Invoke(null, object[] { });
        }
    }
}

Exception: An exception of type 'System.TypeLoadException' occurred in mscorlib.dll but was not handled in user code

Additional information: Nie można załadować typu 'Engine.ModCrew.Mod' z zestawu 'Game, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'.

Then TypeLoadException on "var x3 = x2.Invoke(null, new object[] { });" in Core.cs — TheChilliPL
"An exception of type 'System.TypeLoadException' occurred in mscorlib.dll but was not handled in user code" — TheChilliPL
@TheChilliPL OnStart doesn't take any arguments, do x2.Invoke(null, null); instead — Mathias R. Jessen

dukedukes dukedukes · Accepted Answer · 2016-09-24T15:48:16

You should always use BindingFlags when getting methods via reflection.

Invoking an instance with MethodInfo.Invoke requires the instance as the first parameter MethodInfo.Invoke(MyInstance,...)

Changes based on comments:

public static void Main(string[] args)
{
    Assembly a = Assembly.LoadFile(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "mods\\ExampleMod.dll"));
    var x1 = a.GetType("PTF_Mod.Mod_Main");
    var x2 = x1.GetMethod("OnStart", BindingFlags.Static | BindingFlags.Public);
    var x3 = x2.Invoke(null, null);

    while(true);
}

Mod_Main:

public static void OnStart()
{
    var exe = Assembly.GetCallingAssembly();
    Console.WriteLine(exe.Location); //Location is valid
    var x = exe.GetType("Engine.ModCrew+Mod", true); //But here I get exception
    var y = Activator.CreateInstance(x);

    x.GetMethod("ItWorks", BindingFlags.Instance | BindingFlags.Public).Invoke(y, null);
}

Also, consider if reflection is even necessary, it can make programs overly complicated. If it's necessary you should look into Dynamic to avoid a lot of the troubles of invoking methods with reflection

Assembly.GetType("[...]", true); throws TypeLoadException

1 Answers