加密url发生 Invalid length for a Base-64 char array异常

类是转自：http://forums.asp.net/t/1222829.aspx，但是有些问题，现在把解决方法共享下，很简单的

using System;
using System.IO;
using System.Xml;
using System.Text;
using System.Security.Cryptography; 


/**//// <summary>
/// Summary description for Encryption64
/// </summary>
public class Encryption64
{
    const string DESKey = "AQWSEDRF";
    const string DESIV = "HGFEDCBA";

    public static string DESDecrypt(string stringToDecrypt)//Decrypt the content
    {

        byte[] key;
        byte[] IV;

        byte[] inputByteArray;
        try
        {

            key = Convert2ByteArray(DESKey);

            IV = Convert2ByteArray(DESIV);

            int len = stringToDecrypt.Length;

          //  stringToDecrypt =stringToDecrypt.Replace(" ","+");
            inputByteArray = Convert.FromBase64String(stringToDecrypt);


            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            MemoryStream ms = new MemoryStream();

            CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(key, IV), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);

            cs.FlushFinalBlock();

            Encoding encoding = Encoding.UTF8; return encoding.GetString(ms.ToArray());
        }

        catch (System.Exception ex)
        {

            throw ex;
        }
    }

    public static string DESEncrypt(string stringToEncrypt)// Encrypt the content
    {

        byte[] key;
        byte[] IV;

        byte[] inputByteArray;
        try
        {

            key = Convert2ByteArray(DESKey);

            IV = Convert2ByteArray(DESIV);

            inputByteArray = Encoding.UTF8.GetBytes(stringToEncrypt);
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            MemoryStream ms = new MemoryStream(); CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(key, IV), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);

            cs.FlushFinalBlock();

            string value = Convert.ToBase64String(ms.ToArray());
          //  value = value.Replace("+"," ");

            return value;
        }

        catch (System.Exception ex)
        {

            throw ex;
        }

    }

    static byte[] Convert2ByteArray(string strInput)
    {

        int intCounter; char[] arrChar;
        arrChar = strInput.ToCharArray();

        byte[] arrByte = new byte[arrChar.Length];

        for (intCounter = 0; intCounter <= arrByte.Length - 1; intCounter++)
            arrByte[intCounter] = Convert.ToByte(arrChar[intCounter]);

        return arrByte;
    }



}

以上代码大部分时间运行是正常的，但是加密得出的字符串如果包含"+",用Request.QueryString接收,"+"字符会漏掉，
解密的时候就会报Invalid length for a Base-64 char array异常，所以加密后要替换下

            string value = Convert.ToBase64String(ms.ToArray());
            value = value.Replace("+"," ");

解密时就要替换回来

            stringToDecrypt =stringToDecrypt.Replace(" ","+");
            inputByteArray = Convert.FromBase64String(stringToDecrypt);

希望对您有帮助，弄了好久才发现的。。。