. NET common techniques _c# writing and reading txt files

usingSystem.Text.RegularExpressions; //Offline Data export        Private voidWritetxt (stringstr) {            stringstrFileName =@"\program Files\firexungengcard\firexungeng.txt"; FileInfo file=NewFileInfo (strFileName);            StreamWriter Swriter; if(file. Exists) {Swriter=NewStreamWriter (strFileName,true, Encoding.default);                Swriter.writeline (str);            Swriter.close (); }            Else{file. Create ().                Close (); Swriter=NewStreamWriter (strFileName,true, Encoding.default);                Swriter.writeline (str);            Swriter.close (); }                                }          //return offline data           Private string[] Readtxt () {stringstrFileName =@"\program Files\firexungengcard\firexungeng.txt"; FileInfo file=NewFileInfo (strFileName); if(file. Exists) {stringContent =String.Empty; using(StreamReader sr =NewStreamReader (strFileName)) {Content=Sr.                    ReadToEnd (); }                    //splitting a string                    string[] Strcontentarray = regex.split (content,"\ r \ n", regexoptions.ignorecase); File.                    Delete (); returnStrcontentarray; }                Else{MessageBox.Show ("you don't have data to import."); }                return NULL; }