c# - Comparing strings of text files -

i have 3 text files: file1 file2 , file3 of contain emails. file1 supposed have emails in there, file2 has emails a-m, , file 3 have emails n-z (this not important figure give little context.)

i writing console application program in c# @ these 3 files, , if there email not 1 should be, write masterfile needs added what.

for example, lets have email john@example.com. if found in file1 not in file2, output of masterfile needs "this email needs added file2: john@example.com". if reversed, , email found in file2 not in file1, output should "this email needs added file1: john@example.com"

as part of code, answer looking needs in sort of foreach loop , if statements, little lost in need put in. if please me in figuring out have use in statements appreciate it. if has question of please feel free ask!

//making list file1 list<string> listfullpack = new list<string>(); string line; streamreader sr = new streamreader("file1"); while ((line = sr.readline()) != null) {     listfile1.add(line); } sr.close();  //making list file2 list<string> listden1 = new list<string>(); string line1;  streamreader sr1 = new streamreader("file2"); while ((line1 = sr1.readline()) != null) {     listfile2.add(line1); } sr1.close();  //making list file3 list<string> listden2 = new list<string>(); string line2;  streamreader sr2 = new streamreader("file3"); while ((line2 = sr2.readline()) != null) {     listfile3.add(line2); } sr2.close();  //this double check emails in foreach (string element in listfullpack) {     system.console.writeline(element);     debug.writeline(element);      if (element == "jimbob@example.com")     {          debugger.break();     } }  //this compare file1 list file2 list var firstnotsecond = listfile1.except(listfile2).tolist(); var secondnotfirst = listfile2.except(listfile1).tolist();  //this compare file2 list file3 list var firstnotthird = listfile1.except(listfile3).tolist(); var thirdnotfirst = listfile3.except(listfile1).tolist();  //this compare file2 list file3 list var secondnotthird = listfile2.except(listfile3).tolist(); var thirdnotsecond = listfile3.except(listfile2).tolist();  foreach (string element in listfile1) // lost {     if (!)     {      } } 

you try simple this:

    //making list file1     hashset<string> listfile1 = new hashset<string>();     string line;     streamreader sr = new streamreader("file1");     while ((line = sr.readline()) != null)     {         listfile1.add(line);     }     sr.close();      //making list file2     hashset<string> listfile2 = new hashset<string>();     string line1;     streamreader sr1 = new streamreader("file2");     while ((line1 = sr1.readline()) != null)     {         listfile2.add(line1);     }     sr1.close();      //making list file3     hashset<string> listfile3 = new hashset<string>();     string line2;     streamreader sr2 = new streamreader("file3");     while ((line2 = sr2.readline()) != null)     {         listfile3.add(line2);     }     sr2.close();      ienumerable<string> allemails = listfile1.union(listfile2).union(listfile3);      // double check emails     foreach (string element in allemails)     {         if (!listfile1.contains(element))             system.console.writeline("file 1 missing " + element);          int firstcharascii = element.trim().tolower()[0];         if (firstcharascii < 110)         {             // less "n"             if (!listfile2.contains(element))                 system.console.writeline("file 2 missing " + element);             if (listfile3.contains(element))                 system.console.writeline("file 3 erroneously contains " + element);         }         else         {             // "n" or greater             if (!listfile3.contains(element))                 system.console.writeline("file 3 missing " + element);             if (listfile2.contains(element))                 system.console.writeline("file 2 erroneously contains " + element);         }     } 

keep in mind, number of emails grows large, list<string>.contains() method becomes inefficient way of determining presence or absence. better suited hashset<string> class. also, if whatever reason reading in unicode strings, need more robust method checking first character's value.