字符串的填充、复制与加密和解密

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
    class Program
    {
        //定义静态变量
        static string encryptKey = "Oyea";//定义密钥

        /// <summary>
        /// 加密字符串
        /// </summary>
        /// <param name="str">待加密的字符串</param>
        /// <returns>返回加密的字符串</returns>
       static string Encrypt(string str)
        {
            DESCryptoServiceProvider descsp = new DESCryptoServiceProvider();//实例化加/解密类对象
            byte[] key = Encoding.Unicode.GetBytes(encryptKey);//定义字节数组，用来存储密钥
            byte[] data = Encoding.Unicode.GetBytes(str);//定义字节素组，用来存储要加密的字符串

           //实例化内存流对象
            MemoryStream ms = new MemoryStream();
           
           //使用 内存流实例 实例化 加密流对象
            CryptoStream cstream = new CryptoStream(ms, descsp.CreateEncryptor(key, key), CryptoStreamMode.Write);
            cstream.Write(data, 0, data.Length);//向加密流中写入数据
            cstream.FlushFinalBlock();//释放加密流
            return Convert.ToBase64String(ms.ToArray());
        }

        /// <summary>
        /// 解密字符串
        /// </summary>
        /// <param name="str">待解密的字符串</param>
        /// <returns>返回解密后的字符串</returns>
       static string Decrypt(string str)
       {
           DESCryptoServiceProvider descsp = new DESCryptoServiceProvider();//实例化加/解密类对象
           byte[] key = Encoding.Unicode.GetBytes(encryptKey);//定义字节数组，用来存储密钥
           byte[] data = Convert.FromBase64String(str);//定义字节素组，用来存储要解密的字符串
          
           //实例化内存流对象
           MemoryStream ms = new MemoryStream();

           //使用 内存流实例 实例化 解 密流对象
           CryptoStream cstream = new CryptoStream(ms, descsp.CreateDecryptor(key, key), CryptoStreamMode.Write);
           cstream.Write(data, 0, data.Length);//向加密流中写入数据
           cstream.FlushFinalBlock();//释放加密流
           return Encoding.Unicode.GetString(ms.ToArray());
          // return Encoding.Default.GetString(ms.ToArray());  
       }
        static void Main(string[] args)
        {
            //字符串的填充
            Console.WriteLine("字符串的填充");
            string strFill = "*^__^*";//长度为6，两个下划线
            string strFillLeft = strFill.PadLeft(7, '('); //总长度为7，在左侧用（填充
            string strFillRight = strFillLeft.PadRight(8, ')');//总长度为8，在右侧用）填充
            Console.WriteLine("填充之前：" + strFill);
            Console.WriteLine("左侧填充：" + strFillLeft);
            Console.WriteLine("右侧填充：" + strFillRight);
            Console.WriteLine();

            //字符串的Copy
            Console.WriteLine("字符串的Copy方法");
            string strA = "C#开发实战";
            string strB;
            strB = string.Copy(strA);//string的Copy方法
            Console.WriteLine("原来的字符串：" + strA);
            Console.WriteLine("拷贝后字符串：" + strB);
            Console.WriteLine();

            //字符串的CopyTo
            Console.WriteLine("字符串的CopyTo方法");
            string strC = "C#编程词典";
            char[] myChar = new char[100];
            //str.CopyTo(需要复制的字符串的起始位置，目标字符数组，指定目标数组中的开始存放位置，指定要复制的字符个数);
            strC.CopyTo(2, myChar, 10, 4);
            Console.WriteLine(myChar);//前面有10个空格
            Console.WriteLine();

            //字符串的加密与解密
            Console.WriteLine("请输入要加密的字符串：");
            string strOld = Console.ReadLine();
            Console.WriteLine("待加密的字符串是：" + strOld);
            string strEncrypt = Encrypt(strOld);
            Console.WriteLine("加密后的字符串是：" + strEncrypt);
            string strDecrypt = Decrypt(strEncrypt);
            Console.WriteLine("解密后的字符串是：" + strDecrypt);


            Console.ReadKey();
        }
    }
}

运行结果：