Streamreader reading text file garbled

Solve the Problem of garbled characters in reading text files. I used to determine the text file format before reading.

Streamreader sr = new streamreader (fullfilename, getfileencodetype (fullfilename ))

Public System. text. encoding getfileencodetype (string filename) {system. io. filestream FS = new system. io. filestream (filename, system. io. filemode. open, system. io. fileaccess. read); system. io. binaryreader BR = new system. io. binaryreader (FS); byte [] buffer = BR. readbytes (2); If (buffer [0]> = 0xef) {If (buffer [0] = 0xef & buffer [1] = 0xbb) {return system. text. encoding. utf8;} else if (buffer [0] = 0xfe & buffer [1] = 0xff) {return system. text. encoding. bigendianunicode;} else if (buffer [0] = 0xff & buffer [1] = 0xfe) {return system. text. encoding. unicode;} else {return system. text. encoding. default ;}} if (buffer [0] = 0x3c) // UTF-8 no Bom format {return system. text. encoding. utf8;} else {return system. text. encoding. default ;}}