Some class code of caesar cryptography sample. (http://csharppad.com/gist/b874d4eaf8089322cb2a75db869cbdcd)

caesar cipher.cs

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public class caesar {
    string plain,output;
    int Key;
    
    public caesar(string source, int givenKey) {
        plain = source;
        Key = givenKey;
    }
    
    public void crypt() {
     char[] array =  plain.ToCharArray();
     for (int i = 1; i < array.Length; i++) {
         if (char.IsLetter(array[i])) {
             int c = array[i];
             if (c > 'a' && c < 'z') {
              c = (((c-'a')+ Key) % 26)+'a';
             }
             if (c > 'A' && c < 'Z') {
              c = (((c-'A')+ Key) % 26)+'A';
             }
        
             array[i] = (char)c;
         }
         output = new string(array);
     }
    }
    public void decrypt() {
        char[] array =  plain.ToCharArray();
     for (int i = 1; i < array.Length; i++) {
         if (char.IsLetter(array[i])) {
             int c = array[i];
             if (c > 'a' && c < 'z') {
              c = (((c-'a')- Key) % 26)+'a';
             }
             if (c > 'A' && c < 'Z') {
              c = (((c-'A')- Key) % 26)+'A';
             }
        
             array[i] = (char)c;
         }
         output = new string(array);
     }
    }
    public string GetOutput() {
        return output;
    }
 }