How to Generate a Random String in C#?

We can create random strings in C# using the Random class. The Random class of .NET provides functionality to generate random numbers, strings, and other data types.

The following code example generates a random string of a given length.

using System.Text;

namespace Namespace8
{
    class RandomNumberSample
    {
        static void Main(string[] args)
        {
            var generator = new RandomGenerator();

            var randomString = generator.RandomString(10);
            Console.WriteLine($"Random string of 10 chars is {randomString}");         

            Console.ReadKey();
        }
    }

    public class RandomGenerator
    {
        // Instantiate random number generator.
        // It is better to keep a single Random instance
        // and keep using Next on the same instance.
        private readonly Random _random = new Random();

        // Generates a random string with a given size.
        public string RandomString(int size, bool lowerCase = false)
        {
            var builder = new StringBuilder(size);

            // Unicode/ASCII Letters are divided into two blocks
            // (Letters 65–90 / 97–122):
            // The first group containing the uppercase letters and
            // the second group containing the lowercase.

            // char is a single Unicode character
            char offset = lowerCase ? 'a' : 'A';
            const int lettersOffset = 26; // A...Z or a..z: length = 26

            for (var i = 0; i < size; i++)
            {
                var @char = (char)_random.Next(offset, offset + lettersOffset);
                builder.Append(@char);
            }

            return lowerCase ? builder.ToString().ToLower() : builder.ToString();
        }

       
    }
}

As you can see from the above example, the Random class is the magician. It provides Random.Next(), Random.NextBytes(), and Random.NextDouble() methods. The Random.Next() method returns a random number, Random.NextBytes() returns an array of bytes filled with random numbers and Random.NextDouble() returns a random number between 0.0 and 1.0.

Hope you find this code snippet useful.