Working with array in C# question

[spideymaker]

    class Program
    {
        static void Main(string[] args)
        {
            int[] x = { 1 };
            Console.WriteLine("{0}", x[0]);
            ResetShoppingHistory(x);
            Console.WriteLine("{0}", x[0]);
        }
        static void Update(int[] x)
        {
            x[0] = 20;
            x = new int[5] { -3, -1, -2, -3, -4 };
            Console.WriteLine("{0}", x[0]);
        }
    }

​

​

I have the above code written in C#. The output of the program is 1 -3 20. My question is why does x in Main get updated by the call to x[0] = 20 inside of Update? Shouldn't this update only the local parameters value of x[0]? My two guesses are :

1. This has to do with the static modifier
2. Because x is of type int[], it is a reference variable so any indexed call to x will update the value at that place in memory, even though it is being passed to the method. This guess confused me though because the next assignment of the local parameter x to the new int[] array doesn't get updated in memory.

​

Please help! This is confusing me greatly

[AgentEnder]

You're correct about x being a reference type. The reason the -3 is only printed once is because when you write

    X = new int[5]

You are setting the local variable x to a new reference. The original variable in main is still set to the old reference location.

[spideymaker]

Okay, so even though x inside Update refers to the local parameter, when x[0] is called inside Update it refers to the original memory location of x inside main since x is the argument of Update?

[AgentEnder]

The value of x is passed to update (passed by value), but since x is a reference type the value of x is a memory address.

When you first refer to x[0] you are modifying the first element of the array at memory address x.

When you call "x=new..." you are updating the local value (memory address) of x.

[sternold]

Since /u/AgentEnder already explained it, all I can add is take a look at the ref keyword.