C# arrays use of unassigned local variable

Here in this piece of code I'm trying to add random numbers between 0 to 9, to an array but when I'm trying to assign numbers to the array inside a for loop, I receive this error:

Error 1 Use of unassigned local variable 'x'

Here is the code:

using System;
    class Core
    {
        public static void Main()
        {
            Random rnd = new Random();
            int[] x;
            for (int i = 0; i < 4; i++)
            {
                x[i] = rnd.Next(1, 9);
            }
         }
     }