3des加密为何编译出错?

Question

private static byte[] Keys = {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF};
/// <summary>
/// DES加密字符串
/// </summary>
/// <param name="encryptStr">待加密的字符串</param>
/// <param name="encryptKey">加密密钥,要求为8位</param>
/// <returns>加密成功返回加密后的字符串，失败返回源串</returns>
public static string EncryptDES(string encryptStr,string encryptKey)
{
try
{
byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(0,8));
byte[] rgbIV = Keys;
byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptStr);
DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
MemoryStream mStream = new MemoryStream();
CryptoStream cStream = new CryptoStream(mStream,dCSP.CreateEncryptor(rgbKey,rgbIV),CryptoStreamMode.Write);
cStream.Write(inputByteArray,0,inputByteArray.Length);
cStream.FlushFinalBlock();
return Convert.ToBase64String(mStream.ToArray());
}
catch
{
return encryptStr;
}
} /// <summary>
/// DES解密字符串
/// </summary>
/// <param name="decryptStr">待解密的字符串</param>
/// <param name="decryptKey">解密密钥,要求为8位,和加密密钥相同</param>
/// <returns>解密成功返回解密后的字符串，失败返源串</returns>
public static string DecryptDES(string decryptStr,string decryptKey)
{
try
{
byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey);
byte[] rgbIV = Keys;
byte[] inputByteArray = Convert.FromBase64String(decryptStr);
DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
MemoryStream mStream = new MemoryStream();
CryptoStream cStream = new CryptoStream(mStream,DCSP.CreateDecryptor(rgbKey,rgbIV),CryptoStreamMode.Write);
cStream.Write(inputByteArray,0,inputByteArray.Length);
cStream.FlushFinalBlock();
return Encoding.UTF8.GetString(mStream.ToArray());
}
catch
{
return decryptStr;
}
}