c# - Datareader, not all paths returns a value -

i want make function returns string:

public string lienbasedeconnaissance(string entreprise) {     sqlconnection cnx = new sqlconnection("/* connection string */");     cnx.open();     sqlcommand requeteexiste = new sqlcommand("sp_sel_lien_baseconnaissance_extranet_client", cnx);     requeteexiste.commandtype = commandtype.storedprocedure;      sqlparameter parameter = requeteexiste.parameters.add("@nom_entreprise", sqldbtype.nvarchar, 15);     parameter.value = entreprise;      string lienbaseconnaissance;     sqldatareader _readerlines = requeteexiste.executereader();     while (_readerlines.read())     {         if (_readerlines["parstrp1"].tostring() != null)         {             lienbaseconnaissance = _readerlines["parstrp1"].tostring();             return lienbaseconnaissance;         }         else         {             return null;         }     }     cnx.close();    } 

i select data stored procedure , return string. problem if don't put return after while (), code doesn't return value. need variable lienbaseconnaissance contains data , out of while(), variable in question doesn't have anymore value i'm looking for.

the problem while-loop. it's not if, possible loop never entered if there no rows.

the simplest solution assign default value return variable:

string lienbaseconnaissance = null; // .... @ end of method: return lienbaseconnaissance; 

since (i assume that) reading single value possible:

if(_readerlines.read()) {     if (!_readerlines.isdbnull("parstrp1"))     {         lienbaseconnaissance = _readerlines.getstring("parstrp1");         return lienbaseconnaissance;     }     else     {         return null;     } } else     return null; 

note should use using-statement ensure unmanaged resources disposed (e.g. connection gets closed). use implements idisposable, connection, command , reader.