View difference between Paste ID: GRAfdPwn and M5EELZBp

 static void Main(string[] args)
         {
             Console.WriteLine("Choose action:\n1.Encryption \n2.Decryption");
             int choice = int.Parse(Console.ReadLine());
 
             Console.WriteLine("Submit text");
             string text = Console.ReadLine();
 
             Console.WriteLine("Submit key (1-31)");
             int key = int.Parse(Console.ReadLine());
             if (key < 0)
             {
                 key = 0;
             }
 
             if (choice == 1)
             {
                 string encryptedText = Encryption(text, key);
                 Console.WriteLine($"Encrypted text: {encryptedText}");
             }
             else
             {
                 string decryptedText = Decryption(text, key);
                 Console.WriteLine($"Decrypted text: {decryptedText}");
             }
 
             Console.ReadLine();
 
         }
         public static string Encryption(string text, int key)
         {
             string alphabet = "abcdefghijklmnopqrstuvwxyz";
             string encryptedText = "";
 
             for (int counter = 0; counter < text.Length; counter++)
             {
 
                 char character = text[counter];
 
                 int characterNumber = alphabet.IndexOf(character);
 
                 if (characterNumber == -1)
                 {
                     encryptedText += character;
                 }
                 else
                 {
 
                     int newCharacterNumber = (characterNumber + key) % alphabet.Length;
                     char newCharacter = alphabet[newCharacterNumber];
                     encryptedText += newCharacter;
                 }
             }
 
             return encryptedText;
         }
 
         public static string Decryption(string text, int key)
         {
             string alphabet = "abcdefghijklmnopqrstuvwxyz";
             string decryptedText = "";
 
             for (int counter = 0; counter < text.Length; counter++)
             {
 
                 char character = text[counter];
 
                 int characterNumber = alphabet.IndexOf(character);
 
                 if (characterNumber == -1)
                 {
                     decryptedText += character;
                 }
                 else
                 {
                     int newCharacterNumber = (characterNumber + (alphabet.Length - key)) % alphabet.Length;
                     char newCharacter = alphabet[newCharacterNumber];
                     decryptedText += newCharacter;
                 }
             }
 
             return decryptedText;
         }