将该代码转化当C#窗体程序中using System; namespace VigenereCipher { class Program { static void Main(string[] args) { Console.WriteLine("请选择操作：\n1. 加密\n2. 解密"); int choice = int.Parse(Console.ReadLine()); Console.WriteLine("请输入明文/密文："); string text = Console.ReadLine(); Console.WriteLine("请输入密钥："); string key = Console.ReadLine(); if (choice == 1) { string cipherText = Encrypt(text, key); Console.WriteLine("加密后的结果为：" + cipherText); } else if (choice == 2) { string plainText = Decrypt(text, key); Console.WriteLine("解密后的结果为：" + plainText); } else { Console.WriteLine("输入错误！"); } } static string Encrypt(string text, string key) { string cipherText = ""; int keyIndex = 0; for (int i = 0; i < text.Length; i++) { char c = text[i]; int offset = key[keyIndex] - 'A'; char encryptedChar = (char)((c + offset) % 256); cipherText += encryptedChar; keyIndex = (keyIndex + 1) % key.Length; } return cipherText; } static string Decrypt(string text, string key) { string plainText = ""; int keyIndex = 0; for (int i = 0; i < text.Length; i++) { char c = text[i]; int offset = key[keyIndex] - 'A'; char decryptedChar = (char)((c - offset + 256) % 256); plainText += decryptedChar; keyIndex = (keyIndex + 1) % key.Length; } return plainText; } } }

以下是将该代码转化为C#窗体程序的示例代码：

using System;
using System.Windows.Forms;

namespace VigenereCipher
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void encryptButton_Click(object sender, EventArgs e)
        {
            string text = inputTextBox.Text;
            string key = keyTextBox.Text;

            string cipherText = Encrypt(text, key);

            outputTextBox.Text = cipherText;
        }

        private void decryptButton_Click(object sender, EventArgs e)
        {
            string text = inputTextBox.Text;
            string key = keyTextBox.Text;

            string plainText = Decrypt(text, key);

            outputTextBox.Text = plainText;
        }

        static string Encrypt(string text, string key)
        {
            string cipherText = "";
            int keyIndex = 0;

            for (int i = 0; i < text.Length; i++)
            {
                char c = text[i];
                int offset = key[keyIndex] - 'A';
                char encryptedChar = (char)((c + offset) % 256);
                cipherText += encryptedChar;
                keyIndex = (keyIndex + 1) % key.Length;
            }

            return cipherText;
        }

        static string Decrypt(string text, string key)
        {
            string plainText = "";
            int keyIndex = 0;

            for (int i = 0; i < text.Length; i++)
            {
                char c = text[i];
                int offset = key[keyIndex] - 'A';
                char decryptedChar = (char)((c - offset + 256) % 256);
                plainText += decryptedChar;
                keyIndex = (keyIndex + 1) % key.Length;
            }

            return plainText;
        }
    }
}

在窗体设计器中添加一个`TextBox`控件用于输入明文/密文，一个`TextBox`控件用于输入密钥，一个`TextBox`控件用于显示加密/解密结果，以及两个`Button`控件分别用于加密和解密操作。

然后，将`encryptButton_Click`和`decryptButton_Click`事件处理程序中的代码替换为原来的`Main`方法中的代码即可。注意修改控件的名称以与代码中的名称相匹配。