c# - Why relationship that were set with Fluent API are being lost after restarting app? -


i have 2 classes:

class owner {     [key]     public int ownerid { get; set; }      [required]     public string name { get; set; }      public virtual icollection<car> cars { get; set; }      public owner()     {         cars = new list<car>();     } }  class car {     [key]     public int carid { get; set; }      [required]     public string model { get; set; }      public virtual icollection<owner> owners { get; set; }      public car()     {         owners = new list<owner>();     } }

i setting many many relationship in database context using fluent api:

class carslistdatacontext : dbcontext {     public dbset<owner> owners { get; set; }      public dbset<car> cars { get; set; }      public carslistdatacontext() : base("name=carslistconnectionstring")     {      }      protected override void onmodelcreating(dbmodelbuilder modelbuilder)     {         modelbuilder.entity<car>()                     .hasmany(car => car.owners)                     .withmany(owner => owner.cars);     } }

and run code:

    static void main(string[] args)     {         var dbcontext = new carslistdatacontext();          var owner = new owner()         {             name = "john smith"         };          var car = new car()         {             model = "volkswagen beetle"         };          owner.cars.add(car);         car.owners.add(owner);          dbcontext.owners.add(owner);         dbcontext.cars.add(car);         dbcontext.savechanges();          foreach (var o in dbcontext.owners)         {             string cars = string.empty;             foreach (var c in o.cars)             {                 cars += c.model;             }             console.writeline(o.name + ": " + cars);         }          foreach (var c in dbcontext.cars)         {             string owners = string.empty;             foreach (var o in c.owners)             {                 owners += o.name;             }             console.writeline(c.model + ": " + owners);         }          console.readkey();     }

everything ok, entity framework creates new database , app's output looks like:

john smith: volkswagen beetle volkswagen beetle: john smith

then remove lines add new values database:

static void main(string[] args) {     var dbcontext = new carslistdatacontext();      dbcontext.savechanges();      foreach (var o in dbcontext.owners)     {          string cars = string.empty;          foreach (var c in o.cars)          {               cars += c.model;          }          console.writeline(o.name + ": " + cars);      }       foreach (var c in dbcontext.cars)      {          string owners = string.empty;          foreach (var o in c.owners)          {              owners += o.name;          }          console.writeline(c.model + ": " + owners);       }        console.readkey(); }

if run code, get:

john smith: volkswagen beetle:

so why relationship between owners , cars being lost? using sql server 2012 localdb, if matters.


Comments

Post a Comment

Popular posts from this blog

sql server - Cannot query correctly (MSSQL - PHP - JSON) -

i have little problem on project. , turns out query result returns nothing when value of first name or last name has 'ñ' in it. here's code config.php: <?php ini_set('mssql.charset', 'utf-8'); header('content-type: text/html; charset=utf-8'); $servername = "192.168.1.21"; /* ip add of db server */ $connection = array("database" => "db", "uid" => "?", "pwd" => "***"); $conn = sqlsrv_connect($servername, $connection); if(!$conn){ echo "connection not established."; die(print_r(sqlsrv_errors(), true)); } ?> myquery: $idnumber = $_post["idnum"]; $response = array(); $query2 = "select clname, cfname, cmname, cqualifier student cidno = '$idnumber'"; try{ $stmt2 = sqlsrv_query($conn, $query2); } catch(pdoexeption $ex){ $response["success"] = 0; $response["message"] = "d...
Read more

php - trouble displaying mysqli database results in correct order -

i have table in database stores events , date expire. want display events on website display current events first expired events after? i have tried following sql $sql = "select noticeid, notice, noticedesc, noticeimg, noticedate, expirydate tbl_notices group noticeid ,expired order expirydate asc"; but returns expired results first due expirydate being ordered asc in query. my tbl_notice structure looks this noticeid => int(4) notice => varchar(100) noticedesc => text noticedate => timestamp noticeimg => varchar(40) expirydate => datetime expired => int(1) 0 current or 1 expired my php code is $sql = "select noticeid, notice, noticedesc, noticeimg, noticedate, expirydate tbl_notices group noticeid ,expired order expirydate asc"; $result = mysqli_query($conn,$sql); if ($result->num_rows > 0) { // output data of each row while($row = $result->fetch_assoc()) { ...
Read more

C++ Linked List -

i trying create linked list download txt file , use linked list handle file line line. when handling downloaded linked list operations performed on such text editor would. encountering problems however. seems "node(string value)" section of code has wrong though original node() declaration no arguments passes. unable figure out quite is. node.h class node { public: node(); node(string value); void setnext(node *nextnode); // allows user set "next" pointer of node points friend class linkedlist; private: string data; // data box node* next; // pointer box }; node.cpp # include <string> # include "node.h" using namespace std; node::node() { data = ""; next = null; } node::node(string value) { data = value; next = null; } void node::setnext(node *nextnode) // allows user set "next" pointer of node points { this->next = nextnode; } your #include <string> ...
Read more