using System;

public class Program

{

    public static void Main()

    {

        generateRandomId("chat", 18);

        Console.WriteLine("------------------NEXT EXAMPLE-----------------------");

        generateRandomId("chat", 128);

        Console.WriteLine("------------------NEXT EXAMPLE-----------------------");

        generateRandomId("chat", 150);

        Console.WriteLine("------------------NEXT EXAMPLE-----------------------");

    }

    public static string generateRandomId(string type, int totalLength) {

        string adjustablePart = String.Empty;

        string randomPart = Guid.NewGuid().ToString();

        int availableLength = totalLength - (type.Length + randomPart.Length);

        if (availableLength > 0) {

            adjustablePart = new String('a', availableLength);

        }

​

        string assembled = String.Format("{0}-{1}-{2}", type, adjustablePart, randomPart);

​

        Console.WriteLine("Available Length for type: [{0}] and total length: [{1}] = [{2}]", type, totalLength, availableLength);

        string trimmedToTotalLength =  assembled.Substring(0, totalLength);

        Console.WriteLine("Full ID: [{0}]", trimmedToTotalLength);

        Console.WriteLine("ID Length: [{0}]", trimmedToTotalLength.Length);

        string result = assembled.Substring(0, totalLength);

​

        return result;

    }

}