Is there a way to require that an argument provided to a method is not null?

Question

Is there a better way to require that an argument is not null in a method? I keep checking if any of the arguments that my method requires are null, as show below. But I'm wondering if there is a better way.

public void MyMethod(string a, int b)
{
   if(a==null){throw new ArgumentNullException("a");}
   if(b==null){throw new ArgumentNullException("b");}

   //more stuff here
}

Answer 1

Rick Brewster (author of Paint.NET) blogged about a Fluent API alternative:

http://blog.getpaint.net/2008/12/06/a-fluent-approach-to-c-parameter-validation/

Answer 2

You can write some utility methods. This is the common pattern in java.

user code:

public void MyMethod(string a, int b)
{
    //validate each
    Objects.RequireNotNull(a);
    Objects.RequireNotNull(b);

    //or validate in single line as array 
    Objects.RequireNotNullArray(a, b);
}

implementation code:

public static class Objects
{
    public static T RequireNotNull<T>(T arg)
    {
        if(arg == null)
        {
            throw new ArgumentNullException();
        }
        return arg;
    }

    public static object[] RequireNotNullArray(params object[] args)
    {
        return RequireNotNullArray<object>(args);
    }

    public static T[] RequireNotNullArray<T>(params T[] args)
    {
        Objects.RequireNotNull(args);
        for(int i=0; i<args.Length; i++)
        {
            T arg = args[i];
            if(arg == null)
            {
                throw new ArgumentNullException($"null entry at position:{i}");
            }
        }
        return args;
    }

}

You cannot get the variable name in the exception. but with the stack trace and your source code, it should be possible to easily track down.