How to Declare a Constant Array in C#

This tutorial will discuss methods to declare a constant array in C#.

Declare a Constant Array With the readonly Keyword in C#

In C#, we cannot declare a constant array with the following syntax.

public const string[] Values = { "Value1", "Value2", "Value3", "Value4" };

This will give a compiler error because the const keyword is used for values that are known at the compile-time. But an array does not get initialized during compile-time, so the array’s value is not known during the compile-time.

This error can be avoided by using the readonly keyword in C#. The readonly keyword is used to specify that a variable’s value cannot be modified after initialization. The following code example shows us how we can declare a constant array with the readonly keyword in C#.

using System;

namespace constant_array {
  class Program {
    public static readonly string[] Values = { "Value1", "Value2", "Value3" };
    static void Main(string[] args) {
      foreach (var Value in Values) {
        Console.WriteLine(Value);
      }
    }
  }
}

Output:

Value1
Value2
Value3

In the above code, we declared the constant array Values with the readonly keyword in C#.