获取文件的MD5值

public static string GetFileHash(string filePath, HashType type)
        {
            if (!File.Exists(filePath))
                return string.Empty;

            System.Security.Cryptography.HashAlgorithm hasher;
            switch(type)
            {
                case HashType.SHA1:
                default:
                    hasher = new SHA1CryptoServiceProvider();
                    break;
                case HashType.SHA256:
                    hasher = new SHA256Managed();
                    break;
                case HashType.SHA384:
                    hasher = new SHA384Managed();
                    break;
                case HashType.SHA512:
                    hasher = new SHA512Managed();
                    break;
                case HashType.MD5:
                    hasher = new MD5CryptoServiceProvider();
                    break;
                case HashType.RIPEMD160:
                    hasher = new RIPEMD160Managed();
                    break;
            }
            StringBuilder buff = new StringBuilder();
            try
            {
                using (FileStream f = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read, 8192))
                {
                    hasher.ComputeHash(f);
                    Byte[] hash = hasher.Hash;
                    foreach (Byte hashByte in hash)
                    {
                        buff.Append(string.Format("{0:x2}", hashByte));
                    }
                }
            }
            catch
            {
                return "Error reading file." + new System.Random(DateTime.Now.Second * DateTime.Now.Millisecond).Next().ToString();
            }
            return buff.ToString();
    }
     public enum HashType
        {
            [Description("SHA-1")]
            SHA1,
            [Description("SHA-256")]
            SHA256,
            [Description("SHA-384")]
            SHA384,
            [Description("SHA-512")]
            SHA512,
            [Description("MD5")]
            MD5,
            [Description("RIPEMD-160")]
            RIPEMD160
          
        }