check-null-csharp

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace NullChecking {
    struct NonNull<T>
        where T : class 
    {
        public readonly T Value;

        public NonNull(T value) {
            if (value == null) {
                string message = string.Format("Value cannot be null for parameter with type 'NonNull<{0}>'.", typeof(T).Name);
                throw new ArgumentNullException("value", message);
            }

            this.Value = value;
        }

        public static implicit operator T(NonNull<T> nonNullWrapper) {
            return nonNullWrapper.Value;
        }

        public static implicit operator NonNull<T>(T value) {
            return new NonNull<T>(value);
        }
    }

    struct NonNull {
        public static void Use<TArgument>(NonNull<TArgument> arg, Action<TArgument> action) 
            where TArgument: class
        {
            action(arg.Value);
        }
    }

    class Program {
        static void Main(string[] args) {
            // Print2(null);
            Print2("fllock");
        }

        static void Print(string foo) {
            Console.WriteLine("foo length: {0}", foo.Length);
        }

        static void Print2(NonNull<string> foo) {
            //NonNull.Use(foo, f => {
            //});

            Print(foo);
            foo.Value.ToString();
        }
    }
}