C# Language Create method override


This example shows how to override ToString method in generated class

// create an Assembly and new type
var name = new AssemblyName("MethodOverriding");
var dynAsm = AppDomain.CurrentDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.RunAndSave);
var dynModule = dynAsm.DefineDynamicModule(name.Name, $"{name.Name}.dll");
var typeBuilder = dynModule.DefineType("MyClass", TypeAttributes.Public | TypeAttributes.Class);

// define a new method
var toStr = typeBuilder.DefineMethod(
    "ToString", // name
    MethodAttributes.Public | MethodAttributes.Virtual, // modifiers
    typeof(string), // return type
    Type.EmptyTypes); // argument types
var ilGen = toStr.GetILGenerator();
ilGen.Emit(OpCodes.Ldstr, "Hello, world!");

// set this method as override of object.ToString
typeBuilder.DefineMethodOverride(toStr, typeof(object).GetMethod("ToString"));
var type = typeBuilder.CreateType();

// now test it:
var instance = Activator.CreateInstance(type);