C # Gets the value of the file MD5, SHA1

/// <summary>    ///file Check/// </summary>     Public classFileCheck {/// <summary>        ///calculate the MD5 value of a file/// </summary>        /// <param name= "FileName" >the file name and path to calculate the MD5 value</param>        /// <returns>MD5 value 16 binary string</returns>         Public stringMd5file (stringfileName) {            Try            {                returnHashfile (FileName,"MD5"); }            Catch {                return NULL; }        }        /// <summary>        ///calculate the SHA1 value of a file/// </summary>        /// <param name= "FileName" >the file name and path to calculate the SHA1 value</param>        /// <returns>SHA1 value 16 binary string</returns>         Public stringSha1file (stringfileName) {            Try            {                returnHashfile (FileName,"SHA1"); }            Catch {                return NULL; }        }        /// <summary>        ///computes the hash value of a file/// </summary>        /// <param name= "FileName" >the file name and path to calculate the hash value</param>        /// <param name= "Algname" >algorithm: Sha1,md5</param>        /// <returns>hash Value 16 binary string</returns>        Private stringHashfile (stringFileName,stringalgname) {            if(!System.IO.File.Exists (fileName))return string.            Empty; System.IO.FileStream FS=NewSystem.IO.FileStream (FileName, System.IO.FileMode.Open, System.IO.FileAccess.Read); byte[] Hashbytes =hashdata (FS, algname); Fs.            Close (); returnbytearraytohexstring (hashbytes); }        /// <summary>        ///Calculate hash value/// </summary>        /// <param name= "Stream" >Stream to calculate the hash value</param>        /// <param name= "Algname" >algorithm: Sha1,md5</param>        /// <returns>hash value byte array</returns>        Private byte[] Hashdata (System.IO.Stream Stream,stringalgname)            {System.Security.Cryptography.HashAlgorithm algorithm; if(Algname = =NULL)            {                Throw NewArgumentNullException ("Algname cannot be null"); }            if(string. Compare (Algname,"SHA1",true) ==0) {algorithm=System.Security.Cryptography.SHA1.Create (); }            Else            {                if(string. Compare (Algname,"MD5",true) !=0)                {                    Throw NewException ("Algname can only use SHA1 or MD5"); } algorithm=System.Security.Cryptography.MD5.Create (); }            returnAlgorithm.computehash (stream); }        /// <summary>        ///byte array converted to a string of 16 binary representations/// </summary>        Private stringBytearraytohexstring (byte[] buf) {            returnBitconverter.tostring (BUF). Replace ("-",""); }    }

C # Gets the value of the file MD5, SHA1