c++ cli - How to find given content of node and modify xml file using C++/CLI -

loginsandpasswords.xml looks this:

<?xml version="1.0" encoding="windows-1250"?> <allusers>   <user>     <id>2</id>     <login>a</login>     <password>a</password>   </user>   <user>     <id>5</id>     <login>b</login>     <password>b</password>   </user>   <user>     <id>7</id>     <login>c</login>     <password>c</password>   </user> </allusers> 

at first insert login name loginbox. before add new user want check if login exists in xml file. example check if login named loginbox->text=b exists in xml file. if yes want show messagebox("given login exists choose another"). if no want create new user in xml file given unique login(loginbox->text), given password(passwordbox->text) , id greater max id value of users.

this should help:

private: system::void button1_click(system::object^  sender, system::eventargs^  e) {               //1 validation condition: none textbox can empty              bool emptyrgstbox = false;              if (loginbox->text == ""){ messagebox::show("login box can not empty!"); emptyrgstbox = true; }              if (passwordbox->text == ""){ messagebox::show("password box can not empty!"); emptyrgstbox = true; }               //2 validation condition: check if given passwords same              bool passwordsarethesame = true;              if (passwordbox->text != passwordconfirmationbox->text)              {                  messagebox::show("passwords not same, try again");                  passwordbox->text = "";                  passwordconfirmationbox->text = "";                  passwordsarethesame = false;              }               //3 validation condition: check if given login exists in db              bool logintaken = false;                                                         string ^ strfilename = l"files/loginsandpasswords.xml";              xmldocument ^ docloginsandpasswords = gcnew xmldocument;               if (file::exists(strfilename))              {                  docloginsandpasswords->load(strfilename);                  xmlelement  ^ elm = docloginsandpasswords->documentelement;                  xmlnodelist ^ lstusers = elm->childnodes;                   (int = 0; < lstusers->count; i++)                  {                      if (loginbox->text == lstusers[i]->childnodes[1]->innertext)                      {                          messagebox::show("login exists, choose login");                          logintaken = true;                      }                  }               }              else              {                  messagebox::show(l"the file " + strfilename + l" not found");              }               //checks whether conditions have been met              if (passwordsarethesame == true && emptyrgstbox == false && logintaken==false)              {                  //finding greates id of users                  int maxid = 0;                  if (file::exists(strfilename))                  {                      docloginsandpasswords->load(strfilename);                      xmlelement  ^ elm = docloginsandpasswords->documentelement;                      xmlnodelist ^ lstusers = elm->childnodes;                       (int = 0; < lstusers->count; i++)                      {                          if (maxid < int::parse(lstusers[i]->childnodes[0]->innertext))                              maxid = int::parse(lstusers[i]->childnodes[0]->innertext);                      }                      //messagebox::show("maxid= " + maxid);                      maxid++;                  }                   //adding new user db                   if (file::exists(strfilename))                  {                      docloginsandpasswords->load(strfilename);                       xmlelement ^ element = docloginsandpasswords->createelement(l"user");                      string ^ struser = l"<id>" + maxid + l"</id>" +                          l"<login>" + loginbox->text + l"</login>" +                          l"<password>" + passwordbox->text + "</password>";                       element->innerxml = struser;                      docloginsandpasswords->documentelement->appendchild(element);                       docloginsandpasswords->save(strfilename);                      messagebox::show("user has been added sucessfully!");                       //cleans texboxes                      passwordbox->text = "";                      passwordconfirmationbox->text = "";                      loginbox->text = "";                   }              }   }