تحديات برمجيةالتحدي الثاني - حل التمرين الرابع بلغة C#

using System;

class Program
{
    static void Main(string[] args)
    {
        string S1, S2, S3, S4="";

        Console.Write("Enter S1: ");
        S1 = Console.ReadLine();

        Console.Write("Enter S2: ");
        S2 = Console.ReadLine();

        Console.Write("Enter S3: ");
        S3 = Console.ReadLine();

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

        // Part 1
        Console.WriteLine("The concatenation of S1 and S2 is equal S3? " + (S3.Equals(S1 + S2)));

        // Part 2
        Console.WriteLine("S1 is part of S2 or S1=S2? " + S2.Contains(S1));
        
        // Part 3
        if (S1.Length > S2.Length)
        {
            S4 = S2 + S1;
        }
        
        // Part 4
        if (S2.Length > S1.Length)
        {
            S4 = S1 + S2;
        }
        
        // Part 5
        Console.WriteLine("S2 is part of the second half of S1? " + (S1.IndexOf(S2, S1.Length / 2) != -1));
        
        // Part 6
        Console.Write("The first half characters of S1 are: ");
        for (int i = 0; i < S1.Length / 2; i++)
        {
            Console.Write(S1[i]);
        }

        Console.ReadKey();
    }
}