Array.CreateInstance

This C# method creates typed arrays. It does not require the type to be known at compile-time. It is a factory method.

When calling CreateInstance in a C# program, we must specify the size of the target array. It returns a typed array of the specified size.

Example

In the first section, we create a single-dimensional array of ints. In the second, we create a 2D array. To call Array.CreateInstance, we must pass a Type pointer as the first argument.

using System;

class Program
{
    static void Main()
    {
        // [1] Create a one-dimensional array of integers.
        {
            Array array = Array.CreateInstance(typeof(int), 10);
            int[] values = (int[])array;
            Console.WriteLine(values.Length);
        }
        // [2] Create a two-dimensional array of bools.
        {
            Array array = Array.CreateInstance(typeof(bool), 10, 2);
            bool[,] values = (bool[,])array;
            values[0, 0] = true;
            Console.WriteLine(values.GetLength(0));
            Console.WriteLine(values.GetLength(1));
        }
    }
}
10
10
2

Discussion

Why would we use Array.CreateInstance? A program may not know the type of elements at compile-time. We could pass any Type reference to Array.CreateInstance.

Array.CreateInstance constructs arrays in memory using parameters. We do not need to know element types at compile-time. CreateInstance() returns the abstract base class Array.