c# asp.net 字符串加密解密的类
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Security.Cryptography;
using System.IO;

/// <summary>
/// 密码控制
/// </summary>
public class Class_Password
{
    const string KEY_64 = "VavicApp";//注意了，是8个字符，64位

    const string IV_64 = "VavicApp";

    public Class_Password()
{
//
// TODO: 在此处添加构造函数逻辑
//
    }

    #region EnCode 加密
    /// <summary>
    /// EnCode 加密
    /// </summary>
    /// <param name="str">要加密的字符串</param>
    /// <returns></returns>
   
    public string EnCode(string data)
    {
        byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
        byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);

        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
        int i = cryptoProvider.KeySize;
        MemoryStream ms = new MemoryStream();
        CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey,

byIV), CryptoStreamMode.Write);

        StreamWriter sw = new StreamWriter(cst);
        sw.Write(data);
        sw.Flush();
        cst.FlushFinalBlock();
        sw.Flush();
        return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
    }
    #endregion

    #region DeCode 解密
    /// <summary>
    /// DeCode 解密
    /// </summary>
    /// <param name="str">要解密的字符串</param>
    /// <returns></returns>
    public string DeCode(string data)
    {
        byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
        byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);

        byte[] byEnc;
        try
        {
            byEnc = Convert.FromBase64String(data);
        }
        catch
        {
            return null;
        }

        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
        MemoryStream ms = new MemoryStream(byEnc);
        CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey,

byIV), CryptoStreamMode.Read);
      &n