ASP.net自带了一个MD5和SHA1加密类库！
下面是调用此类库的两种加密方法：

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public string GetMD5(string strData)
{
//使用MD5加密方法：
System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
byte[] md5Bytes = System.Text.Encoding.Default.GetBytes(strData);
byte[] cryString = md5.ComputeHash(md5Bytes);
string md5Str = string.Empty;
for (int i=0;i<cryString.Length;i++)
{
md5Str += cryString[i].ToString("X2");
}
return md5Str;
}

public string GetEncrypt(string strData,string strType)
{
//使用MD5或SHA1的加密方法：
string strCryData = string.Empty;
if (strType.ToUpper() == "SHA1")
{
strCryData = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(strData,"SHA1");
}
else if (strType.ToUpper() == "MD5")
{
strCryData = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(strData,"MD5");
}
return strCryData;
}