using System;

using System.Linq;

using System.Text;

public class Program

{

    private static string RandomString(int size)

    {

        var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

        var random = new Random();

        var result = new string(

        Enumerable.Repeat(chars, size)

              .Select(s => s[random.Next(s.Length)])

              .ToArray());

        return result;

    }

​

    public static void Main()

    {

        string r = RandomString(10);

        Console.WriteLine(r);

    }

}