c#md5与SHA1验证函数

/// <summary>
        /// MD5验证函数
        /// </summary>
        /// <param name="fileName">文件的路径</param>
        /// <param name="blockletter">返回的MD5值是否为大写</param>
        /// <returns></returns>
        public static string GetMD5HashFromFile(string fileName,bool blockletter)
        {
            try
            {
                FileStream file = new FileStream(fileName, FileMode.Open);
                System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
                byte[] retVal = md5.ComputeHash(file);
                file.Close();

                StringBuilder sb = new StringBuilder();
                for (int i = 0; i < retVal.Length; i++)
                {
                    if (blockletter)
                        sb.Append(retVal[i].ToString("X2"));
                    else 
                        sb.Append(retVal[i].ToString("x2"));
                }
                return sb.ToString();
            }
            catch (Exception ex)
            {
                return "文件读取错误";
            }
        }
        /// <summary>
        ///   计算SHA1值
        /// </summary>
        /// <param name="fileName">文件地址</param>
        /// <param name="blockletter">是否输出大写</param>
        /// <returns></returns>
        public static string GetSHA1HashFromFile(string fileName, bool blockletter)
        {
            var tragetFile = new System.IO.FileStream(fileName, System.IO.FileMode.Open);
            var sha1 = new System.Security.Cryptography.SHA1CryptoServiceProvider();
            byte[] hashbytes = sha1.ComputeHash(tragetFile);
            tragetFile.Close();

            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            for (int i = 0; i < hashbytes.Length; i++)
            {
                if (blockletter) //判断输出大小写
                    sb.Append(hashbytes[i].ToString("X2"));
                else
                    sb.Append(hashbytes[i].ToString("x2"));
            }
            return sb.ToString();
        }