Late binding with assembly

Question

I try to make an example of late binding. So that I understand better the difference between early binding and late binding. I try it like this:

using System;
using System.Reflection;

namespace EarlyBindingVersusLateBinding
{
    class Program
    {
        static void Main(string[] args)
        {
            Customer cust = new Customer();


            Assembly hallo = Assembly.GetExecutingAssembly();

            Type CustomerType = hallo.GetType("EarlyBindingVersusLateBinding.cust");

            object customerInstance = Activator.CreateInstance(CustomerType);

            MethodInfo getFullMethodName = CustomerType.GetMethod("FullName");

            string[] paramaters = new string[2];
            paramaters[0] = "Niels";
            paramaters[1] = "Ingenieur";

            string fullname = (string)getFullMethodName.Invoke(customerInstance, paramaters);



            Console.WriteLine(fullname);
            Console.Read();

        }
    }

    public class Customer
    {

        public string FullName(string firstName, string lastName)
        {

            return firstName + " " + lastName;

        }

    }
}

but I get this exception:

An unhandled exception of type 'System.ArgumentNullException' occurred in mscorlib.dll

Additional information: Value cannot be null.

on this line:

 object customerInstance = Activator.CreateInstance(CustomerType);

And I can't figure out how to fix that.

Thank you.

Well, could you check, whether the variable CustomerType is null? Judging by the error it most likely is. So then the question is why hallo.GetType("EarlyBindingVersusLateBinding.cust"); returns null. Most likely scenario is, that the name of the type is different. (Also I don't know of the bat, whether GetType allows relative Namespace path's) You could use hallo.GetTypes() and list each Type within the assembly to learn more. — MrPaulch
It will be very obvious when you spend a bit of time to debug the code. Assembly.GetType() returns null if you pass the wrong string. Kaboom is next. Consider "Customer" instead of "cust". What made you type "cust" is probably the real question, hard to guess. — Hans Passant

Heinzi Heinzi · Accepted Answer · 2017-05-20T13:01:59

So, Assembly.GetType apparently returned null. Let's check the documentation and find out what that means:

Return Value
Type: System.Type
A Type object that represents the specified class, or null if the class is not found.

So, the class EarlyBindingVersusLateBinding.cust could not be found. This is not surprising, since this is not a valid type in your assembly. cust is a local variable in your Main method. You probably wanted to write:

Type CustomerType = hallo.GetType("EarlyBindingVersusLateBinding.Customer");

Late binding with assembly

1 Answers