Is there a way to build a new type during Runtime?

Question

I am going to ask a question that might sound weird.

Is there a way to build a new class during Runtime? Or at least, add a new property to an existing class.

I mean creating a class that doesn't exist and not an instance of an existing class. I could later on use reflections to load and use this class.

Answer 1

Adding a property to an existing type is not possible, but you can create a new type at runtime using Reflection.Emit. It's pretty complicated stuff, and it goes something like this:

AssemblyBuilder assemblyBuilder = Thread.GetDomain().DefineDynamicAssembly(       assemblyName , AssemblyBuilderAccess.Run, assemblyAttributes); ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("ModuleName"); TypeBuilder typeBuilder = moduleBuilder.DefineType(       "MyNamespace.TypeName" , TypeAttributes.Public);  typeBuilder.DefineDefaultConstructor(MethodAttributes.Public);  // Add a method newMethod = typeBuilder.DefineMethod("MethodName" , MethodAttributes.Public);  ILGenerator ilGen = newMethod.GetILGenerator();  // Create IL code for the method ilGen.Emit(...);  // ...  // Create the type itself Type newType = typeBuilder.CreateType(); 

This code is just a sample. It could contain errors.

You can also generate classes by compiling C# source code at runtime using System.CodeDom, but I don't know a lot about that.

Answer 2

Take a look at the System.Reflection.Emit namespace. I've never used it myself but the classes in this namespace can be used to generate IL (intermediate language).