c#对文件进行MD5加密校验

 public static string GetFileMd5Hash(string strFileFullPath)
            {
                // Create a new instance of the MD5CryptoServiceProvider object.

               System.IO.FileStream fst = null;
                try
                {

                    fst = new System.IO.FileStream(strFileFullPath, System.IO.FileMode.Open);
                    System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
                    // Convert the input string to a byte array and compute the hash.
                    byte[] data =md5 .ComputeHash(fst);

                    // Create a new Stringbuilder to collect the bytes
                    // and create a string.
                    StringBuilder sBuilder = new StringBuilder();

                    // Loop through each byte of the hashed data
                    // and format each one as a hexadecimal string.
                    for (int i = ; i < data.Length; i++)
                    {
                        sBuilder.Append(data[i].ToString("x2"));
                    }

                    fst.Close();
                    // Return the hexadecimal string.
                    return sBuilder.ToString().ToLower();
                }
                catch (System.Exception ex)
                {
                    if (fst != null)
                        fst.Close();
                    return "";
                }
                finally
                {
                }
            }