C# - Is it possible to have null params?

Solution 1:

Absolutely - you can call it with an argument of type string[] with a value of null:

string[] array = null;
Foo(array);

Solution 2:

I decided to write some code up to test this for myself. Using the following program:

using System;

namespace TestParams
{
    class Program
    {
        static void TestParamsStrings(params string[] strings)
        {
            if(strings == null)
            {
                Console.WriteLine("strings is null.");
            }
            else
            {
                Console.WriteLine("strings is not null.");
            }
        }

        static void TestParamsInts(params int[] ints)
        {
            if (ints == null)
            {
                Console.WriteLine("ints is null.");
            }
            else
            {
                Console.WriteLine("ints is not null.");
            } 
        }

        static void Main(string[] args)
        {
            string[] stringArray = null;

            TestParamsStrings(stringArray);
            TestParamsStrings();
            TestParamsStrings(null);
            TestParamsStrings(null, null);

            Console.WriteLine("-------");

            int[] intArray = null;

            TestParamsInts(intArray);
            TestParamsInts();
            TestParamsInts(null);
            //TestParamsInts(null, null); -- Does not compile.
        }
    }
}

The following results are yielded:

strings is null.
strings is not null.
strings is null.
strings is not null.
-------
ints is null.
ints is not null.
ints is null.

So yes, it is entirely possible for the array associated with params to be null.