c# - public string's value is always null -

i started learning c# few days ago , i'm having problem public strings, i'm trying write program copies , replaces files practice i'm having problem public strings no matter how try change code couldn't figure out myself came here help

what doing wrong?

here's code:

namespace extractor {     public partial class form1 : form     {         public string s         {             get;             set;         }         public string sselectedpath         {             get;             set;         }         public string beckup         {             get;             set;         }         public form1()         {             initializecomponent();         }         private void direc_click(object sender, eventargs e)         {             folderbrowserdialog fbd = new folderbrowserdialog();             fbd.description = "select folder";
          if (fbd.showdialog() == dialogresult.ok)         {             string sselectedpath = fbd.selectedpath;         }      }      private void choof_click(object sender, eventargs e)     {         openfiledialog choofdlog = new openfiledialog();         choofdlog.filter = "all files (*.*)|*.*";         choofdlog.filterindex = 1;         choofdlog.multiselect = true;          if (choofdlog.showdialog() == dialogresult.ok)         {              string s = choofdlog.filename;         }      }      private void button3_click(object sender, eventargs e)     {         replacefile( s, sselectedpath, beckup);     }      public static void replacefile(string filetomoveanddelete, string filetoreplace, string backupoffiletoreplace)     {         file.replace(filetomoveanddelete, filetoreplace, backupoffiletoreplace, false);      }      private void button1_click(object sender, eventargs e)     {         folderbrowserdialog fbb = new folderbrowserdialog();         fbb.description = "select folder";          if (fbb.showdialog() == dialogresult.ok)         {             string beckup = fbb.selectedpath;         }     } } 

your mistake here :

if (choofdlog.showdialog() == dialogresult.ok) {     string sselectedpath = choofdlog.filename; } 

you're using local variable, not member variable. so, write :

if (choofdlog.showdialog() == dialogresult.ok) {     sselectedpath = choofdlog.filename; } 

or, better, if doesn't want make mistake, use this. when write member variable or method :

if (choofdlog.showdialog() == dialogresult.ok) {     this.sselectedpath  = choofdlog.filename; }