Why does this work? Executing method from IL without instance
.net, c#, il
Solution
`this` is implemented as a normal parameter; your code simply passes `null` as this parameter.
The only reason that this would normally throw a `NullReferenceException` is that methods are usually called using the `CallVirt` instruction, which does a vtable lookup on the `this` parameter and throws if it's null.
If you use `call`, the method will execute perfectly fine even if `this` is null, although the method itself will likely end up throwing later.
Problem
I was looking through What's the strangest corner case you've seen in C# or .NET?, and this code made me think a little: ``` public class Program { delegate void HelloDelegate(Strange bar); [STAThread()] public static void Main(string[] args) { Strange bar = null; var hello = new DynamicMethod("ThisIsNull", typeof(void), new[] { typeof(Strange) }, typeof(Strange).Module); ILGenerator il = hello.GetILGenerator(256); il.Emit(OpCodes.Ldarg_0); var foo = typeof(Strange).GetMethod("Foo"); il.Emit(OpCodes.Call, foo); il.Emit(OpCodes.Ret); var print = (HelloDelegate)hello.CreateDelegate(typeof(HelloDelegate)); print(bar); Console.ReadLine(); } internal sealed class Strange { public void Foo() { Console.WriteLine(this == null); } } } ``` I do understand what the code does, but I do not understand why it works. Isn't that like doing `null.Foo()`? It works as if `Foo()` is static, and this is being called instead: `Strange.Foo();`. Would you please tell me what I am missing?