C#的md5算法与ASP有所差异。这方面的资料在网上还是比较少有。给你一个可以兼容ASP的md5函数。
private string HexToMd5(string str, int mode) {
string strHex = "";
string str = textBox1.Text;
MD5CryptoServiceProvider md = new MD5CryptoServiceProvider();
byte[] result = md.ComputeHash(Encoding.Default.GetBytes(str));
for (int i = 0; i < 16; i++) {
strHex += String.Format("{0:x2}", result[i]);
}
return (mode == 16) ? strHex.Substring(8, 16) : strHex;
}