asp.net mvc 4 - the process cannot access the file 'xxx.xml' because it is being used by another process -

i googled lot, dint solution problem. iam trying add node in xxx.xml file, throwing error "the process cannot access file 'xxx.xml' because being used process", below class

public class registration { list users; list newusers; string userpath = string.empty; string newuserpath = string.empty; string strusername = string.empty;

    public bool findusername(string firstname, string lastname, string emailaddress, string country, string purchasedate, string username, string password)     {         //put code offers database offers variable         if (readxml(firstname, lastname, emailaddress, country, purchasedate, username, password))             return true;         else             return false;     }      //bool readxml(xmldocument xmlfile2)     bool readxml(string firstname, string lastname, string emailaddress, string country, string purchasedate, string username, string password)     {         try         {             xmldocument receivedxml = new xmldocument();             userpath = httpcontext.current.server.mappath("/sampledata/registration.xml");             newuserpath = httpcontext.current.server.mappath("/sampledata/newregistration.xml");              xmlreadersettings xrs = new xmlreadersettings();             xrs.dtdprocessing = dtdprocessing.ignore;             xmlreader xr = xmlreader.create(userpath, xrs);             if (xr != null)             {                 //setting root element                 xmlrootattribute xroot = new xmlrootattribute();                 xroot.elementname = "registration";                 xroot.isnullable = true;                  xmlserializer deserializer = new xmlserializer(typeof(registration), xroot);                 registration userdetails = (registration)deserializer.deserialize(xr);                 users = userdetails.users;                  foreach (var varuser in users)                 {                     if (username == varuser.username)                     {                         strusername = varuser.username;                         return true;                     }                 }                 if (strusername == "")                 {                     //here iam trying add node xml                     using (streamwriter sw = new streamwriter(file.create(userpath)))                     {                         sw.write("<user><firstname>"                                 + firstname + "</firstname><lastname>"                                 + lastname + "</lastname><country>"                                 + country + "</country><purchasedate>"                                 + purchasedate + "</purchasedate><emailaddress>"                                 + emailaddress + "</emailaddress><username>"                                 + username + "</username><password>"                                 + password + "</password></user>");                     }                     return false;                 }             }             return false;         }         catch (exception)         {             return false;         }     } } 

thanks in advance...

it looks never closing reader, need call xr.close() @ point. or johan suggested, wrap in using statement:

    using (xmlreader xr = xmlreader.create(userpath, xrs))     {         //setting root element         xmlrootattribute xroot = new xmlrootattribute();         xroot.elementname = "registration";         xroot.isnullable = true;          xmlserializer deserializer = new xmlserializer(typeof(registration), xroot);         registration userdetails = (registration)deserializer.deserialize(xr);         users = userdetails.users;          foreach (var varuser in users)         {             if (username == varuser.username)             {                 strusername = varuser.username;                 return true;             }         }         if (strusername == "")         {             //here iam trying add node xml             using (streamwriter sw = new streamwriter(file.create(userpath)))             {                 sw.write("<user><firstname>"                         + firstname + "</firstname><lastname>"                         + lastname + "</lastname><country>"                         + country + "</country><purchasedate>"                         + purchasedate + "</purchasedate><emailaddress>"                         + emailaddress + "</emailaddress><username>"                         + username + "</username><password>"                         + password + "</password></user>");             }             return false;         }     } 

also note: notice method named readxml, yet writing xml in method. can confusing, reading or writing? part of issue may opening file reading, , creating file writing?? have not dealt c# xml libs before doesn't seem right here. might consider breaking down more.