c# - How can I edit numbers in my .txt file? -

i have code here , based on user input, i'd change line of choice have selected. however, can temporarily change line of text , when write out file again, text had not overwritten permanently.

here's code:

public struct classmates {     public string first;     public string last;     public int id; }   static classmates[] readclassmates(classmates[] classmateinfo) {     streamreader sr = new streamreader(@"c:\class.txt");     int count = 0;     while (!sr.endofstream)     {         classmateinfo[count].first = sr.readline();         classmateinfo[count].last = sr.readline();         string idtemp = sr.readline();         classmateinfo[count].id = convert.toint32(idtemp);         count++;     }     sr.close();     return classmateinfo;                }  static void editclassmates(classmates[] classmateinfo) {     console.write("who's number change? ");     string classmateinput = console.readline();     (int = 0; < classmateinfo.length; i++)     {         if (classmateinfo[i].first.equals(classmateinput))         {             console.write("enter new number: ");             string temp = console.readline();             int classmatenumber = convert.toint32(temp);             classmateinfo[i].id = classmatenumber;             console.writeline("you have changed {0}'s number {1}.", classmateinfo[i].first,classmateinfo[i].id.tostring());         }     } }  static void main() {     classmates[] classmateinfo = new classmates[43];      listclassmates(classmateinfo);     editclassmates(classmateinfo);     listclassmates(classmateinfo); } 

i know meant use file.writealltext(), don't know how utilize snippet code.

maybe you're expecting easy answer require custom code need think yourself. if you're linq , want use file.writealltext() method can use oneliner wrote you, haven't tested:

file.writealltext(@"c:\class.txt", string.join(environment.newline, (from cm in classmateinfo select string.format("{1}{0}{2}{0}{3}", environment.newline, cm.first, cm.last, cm.id)).toarray())); 

which creates string array classmateinfo, concatenates array using newline separator , write entire string specified file.