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• Changing models in django results in broken database?

  - by Rhubarb

  I have added and removed fields in my models.py file and then run manage.py syncdb. Usually I have to quit out of the shell and restart it before syncdb does anything. And then even after that, I am getting errors when trying to access the admin pages, it seems that certain new fields that I've added still don't show up in the model: Caught an exception while rendering: no such column: mySite_book.Title

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• Help with chat server

  - by mithun1538

  I am designing a chat server in java. The communication is Http based and not socket based. In the client side I have an applet. In the server side I have a servlet. Applet: I create a new thread to listen for incoming messages(GET method). The main thread is used to send messages(POST messages). The partial code is : public void start() { System.out.println("Creating new thread"); Thread thread = new Thread(this); thread.start(); } private String getNewMessage() { System.out.println("Inside getNewMessage"); String msg = null; try { while(msg == null) { System.out.println("Trying to listen to servlet"); URL servlet = new URL(getCodeBase(), "NewServlet?mode=msg"); URLConnection con = servlet.openConnection(); con.setUseCaches(false); DataInputStream din = new DataInputStream(new BufferedInputStream(con.getInputStream())); msg = din.readUTF(); System.out.println("message read :" + msg); } } catch (Exception e) { e.printStackTrace(); } return msg + "\n"; } public void run() { System.out.println("Inside new thread"); while(true) { System.out.println("inside first while"); String newMsg = getNewMessage(); chatOutput.append(newMsg); System.out.println("Appended!!"); } } private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { String message = chatInput.getText(); chatInput.setText(""); chatOutput.append(message + "\n"); try { System.out.println("Trying to send msg :" + message); URL url = new URL(getCodeBase(), "NewServlet"); URLConnection servletConnection = url.openConnection(); servletConnection.setDoInput(true); servletConnection.setDoOutput(true); servletConnection.setUseCaches(false); servletConnection.setRequestProperty("Content-Type", "application/octet-stream"); ObjectOutputStream out = new ObjectOutputStream(servletConnection.getOutputStream()); out.writeObject(message); out.flush(); out.close(); System.out.println("Message sent!"); } catch (Exception e) { e.printStackTrace(); } } This next code is from the servlet side. it uses the Observable interface to identify and send messages to clients. public class NewServlet extends HttpServlet { // getNextMessage() returns the next new message. // It blocks until there is one. public String getNextMessage() { // Create a message sink to wait for a new message from the // message source. System.out.println("inside getNextMessage"); return new MessageSink().getNextMessage(source);} @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Inside Doget"); response.setContentType("text/plain"); PrintWriter out = response.getWriter(); out.println(getNextMessage()); } // broadcastMessage() informs all currently listening clients that there // is a new message. Causes all calls to getNextMessage() to unblock. public void broadcastMessage(String message) { // Send the message to all the HTTP-connected clients by giving the // message to the message source source.sendMessage(message); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Inside DoPost"); try { ObjectInputStream din= new ObjectInputStream(request.getInputStream()); String message = (String)din.readObject(); System.out.println("received msg"); if (message != null) broadcastMessage(message); System.out.println("Called broadcast"); // Set the status code to indicate there will be no response response.setStatus(response.SC_NO_CONTENT); } catch (Exception e) { e.printStackTrace(); } } /** * Returns a short description of the servlet. * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } MessageSource source = new MessageSource();} class MessageSource extends Observable { public void sendMessage(String message) { System.out.println("inside sendMsg"); setChanged(); notifyObservers(message); } } class MessageSink implements Observer { String message = null; // set by update() and read by getNextMessage() // Called by the message source when it gets a new message synchronized public void update(Observable o, Object arg) { // Get the new message message = (String)arg; // Wake up our waiting thread notify(); } // Gets the next message sent out from the message source synchronized public String getNextMessage(MessageSource source) { // Tell source we want to be told about new messages source.addObserver(this); System.out.println("AddedObserver"); // Wait until our update() method receives a message while (message == null) { try { wait(); } catch (Exception ignored) { } } // Tell source to stop telling us about new messages source.deleteObserver(this); // Now return the message we received // But first set the message instance variable to null // so update() and getNextMessage() can be called again. String messageCopy = message; message = null; System.out.println("Returning msg"); return messageCopy; } } As you can see I have included System.out.println("Some message"); in some places. this was just for debugging purposes. In java console, i get the following output: Creating new thread Inside new thread. inside first while. Inside getNewMessage. Trying to listen to servlet. In the servlet side, i get the following output in the tomcat logs: Inside Doget. inside getNextMessage. AddedObserver. After i type a message in the applet, and send it, I get the foll output in java console: Trying to send msg :you deR?? Message sent! But in servlet side, I dont get anything in the logs. I used the O'Reily Java Servlet Programming as reference(The observer interface comes from there). But I am not getting any chat communication between two clients. As can be understood from the logs, the POST method is not called. Any reason for this?

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• Java synchronized seems ignored

  - by viraptor

  Hi, I've got the following code, which I expected to deadlock after printing out "Main: pre-sync". But it looks like synchronized doesn't do what I expect it to. What happens here? import java.util.*; public class deadtest { public static class waiter implements Runnable { Object obj; public waiter(Object obj) { this.obj = obj; } public void run() { System.err.println("Thead: pre-sync"); synchronized(obj) { System.err.println("Thead: pre-wait"); try { obj.wait(); } catch (Exception e) { } System.err.println("Thead: post-wait"); } System.err.println("Thead: post-sync"); } } public static void main(String args[]) { Object obj = new Object(); System.err.println("Main: pre-spawn"); Thread waiterThread = new Thread(new waiter(obj)); waiterThread.start(); try { Thread.sleep(1000); } catch (Exception e) { } System.err.println("Main: pre-sync"); synchronized(obj) { System.err.println("Main: pre-notify"); obj.notify(); System.err.println("Main: post-notify"); } System.err.println("Main: post-sync"); try { waiterThread.join(); } catch (Exception e) { } } } Since both threads synchronize on the created object, I expected the threads to actually block each other. Currently, the code happily notifies the other thread, joins and exits.

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• jump search algorithm

  - by davit-datuashvili

  i am doing jump search algorithm but it show me that element is not in array while it is here is code import java.math.*; public class jamp { public static int min(int a,int b){ return a } public static void main(String[]args){ int a[]=new int[]{3,7,9,12,14,15,16,17,18}; int l=14; System.out.println(jumpsearch(a,a.length,l)); } public static int jumpsearch(int a[],int n, int l ){ int t=0; int b=(int)Math.sqrt(n); while (a[min(b,n)-1]=n) return -1 ; } while (a[t] return -1 ; if ( a[t]==l) { return t; } } return -1; } } please help

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• Invoke "internal extern" constructor using reflections

  - by Riz

  Hi, I have following class (as seen through reflector) public class W : IDisposable { public W(string s); public W(string s, byte[] data); // more constructors [MethodImpl(MethodImplOptions.InternalCall)] internal extern W(string s, int i); public static W Func(string s, int i); } I am trying to call "internal extern" constructor or Func using reflections MethodInfo dynMethod = typeof(W).GetMethod("Func", BindingFlags.Static); object[] argVals = new object[] { "hi", 1 }; dynMethod.Invoke(null, argVals); and Type type = typeof(W); Type[] argTypes = new Type[] { typeof(System.String), typeof(System.Int32) }; ConstructorInfo cInfo = type.GetConstructor(BindingFlags.InvokeMethod | BindingFlags.NonPublic, null, argTypes, null); object[] argVals = new object[] { "hi", 1 }; dynMethod.Invoke(null, argVals); unfortunantly both variants rise NullReferenceException when trying to Invoke, so, I must be doing something wrong?

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• Java Generics name clash, method not correctly overriden

  - by Shervin

  Hi. I have seen different questions regarding this, but I still find this topic to be very confusing. All I want to do, is have an abstract class that implements an interface, and have a class extending this abstract class so that the hard class needs to implement getKommune() and setKommune(Kommune kommune), but not the other method, because that is in the abstract class. I have the following interface. public interface KommuneFilter { <E extends AbstractKommune<?>> void addKommuneFromCurrentUser(E e); Kommune getKommune(); void setKommune(Kommune kommune); } And this Abstract class public abstract class AbstractKommune<E extends AbstractKommune<?>> implements KommuneFilter { @PrePersist void addKommuneFromCurrentUser(E e) { } } And I want to use it like this public class Person extends AbstractKommune<Person> { private Kommune kommune; public void setKommune(Kommune kommune) {this.kommune=kommune;} public Kommune getKommune() {return kommune;} } However, I get Name clash: The method of has the same erasure of type but does not override it Why isn't it correctly overriden?

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• How do I run all my PHPUnit tests?

  - by JJ

  I have script called Script.php and tests for it in Tests/Script.php, but when I run phpunit Tests it does not execute any tests in my test file. How do I run all my tests with phpunit? PHPUnit 3.3.17, PHP 5.2.6-3ubuntu4.2, latest Ubuntu Output: $ phpunit Tests PHPUnit 3.3.17 by Sebastian Bergmann. Time: 0 seconds OK (0 tests, 0 assertions) And here are my script and test files: Script.php <?php function returnsTrue() { return TRUE; } ?> Tests/Script.php <?php require_once 'PHPUnit/Framework.php'; require_once 'Script.php' class TestingOne extends PHPUnit_Framework_TestCase { public function testTrue() { $this->assertEquals(TRUE, returnsTrue()); } public function testFalse() { $this->assertEquals(FALSE, returnsTrue()); } } class TestingTwo extends PHPUnit_Framework_TestCase { public function testTrue() { $this->assertEquals(TRUE, returnsTrue()); } public function testFalse() { $this->assertEquals(FALSE, returnsTrue()); } } ?>

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• Convert a byte array to a class containing a byte array in C#

  - by Mathijs

  I've got a C# function that converts a byte array to a class, given it's type: IntPtr buffer = Marshal.AllocHGlobal(rawsize); Marshal.Copy(data, 0, buffer, rawsize); object result = Marshal.PtrToStructure(buffer, type); Marshal.FreeHGlobal(buffer); I use sequential structs: [StructLayout(LayoutKind.Sequential)] public new class PacketFormat : Packet.PacketFormat { } This worked fine, until I tried to convert to a struct/class containing a byte array. [StructLayout(LayoutKind.Sequential)] public new class PacketFormat : Packet.PacketFormat { public byte header; public byte[] data = new byte[256]; } Marshal.SizeOf(type) returns 16, which is too low (should be 257) and causes Marshal.PtrToStructure to fail with the following error: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. I'm guessing that using a fixed array would be a solution, but can it also be done without having to resort to unsafe code?

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• C++: Dependency injection, circular dependency and callbacks

  - by Jonathan

  Consider the (highly simplified) following case: class Dispatcher { public: receive() {/*implementation*/}; // callback } class CommInterface { public: send() = 0; // call } class CommA : public CommInterface { public: send() {/*implementation*/}; } Various classes in the system send messages via the dispatcher. The dispatcher uses a comm to send. Once an answer is returned, the comm relays it back to the dispatcher which dispatches it back to the appropriate original sender. Comm is polymorphic and which implementation to choose can be read from a settings file. Dispatcher has a dependency on the comm in order to send. Comm has a dependency on dispatcher in order to callback. Therefor there's a circular dependency here and I can't seem to implement the dependency injection principle (even after encountering this nice blog post).

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• Android app crashes when I change the default xml layout file to another

  - by mib1413456

  I am currently just starting to learn android development and have created a basic "Hello world" app that uses "activity_main.xml" for the default layout. I tried to create a new layout xml file called "new_layout.xml" with a text view, a text field and a button and did the following changes in the MainActivity.java file: setContentView(R.layout.new_layout); I did nothing else expect for adding a new_layout.xml in the res/layout folder, I have tried restarting and cleaning the project but nothing. Below is my activity_main.xml file, new_layout.xml file and MainActivity.java activity_main.xml: <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="org.example.androidsdk.demo.MainActivity" tools:ignore="MergeRootFrame" /> new_layout.xml: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="TextView" /> <EditText android:id="@+id/editText1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:ems="10" > <requestFocus /> </EditText> <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Button" /> MainActivity.java file package org.example.androidsdk.demo; import android.app.Activity; import android.app.ActionBar; import android.app.Fragment; import android.os.Bundle; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.os.Build; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.new_layout); if (savedInstanceState == null) { getFragmentManager().beginTransaction() .add(R.id.container, new PlaceholderFragment()) .commit(); } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } /** * A placeholder fragment containing a simple view. */ public static class PlaceholderFragment extends Fragment { public PlaceholderFragment() { } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_main, container, false); return rootView; } } }

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• C# Sharp: Partial Classes

  - by dcolumbus

  This is quick confirmation question: In order to make partial classes work, I initially thought that there would be a main Class public class ManageDates and then you would create partial classes like public partial class ManageDates to extend the ManageDates class. But from some experiementing, I've come to find out that if you're going to use partial classes, each individual class must be declared public partial class [ClassName] ... Am I correct in this conclusion?

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• how do i load a csv file in rails from a migrate usiing load data local infile ?

  - by Chris Drappier

  Hi All, I have my csv file in my public folder, and i'm trying to load it from a migration, but I get a file not found error using this script : ActiveRecord::Base.connection.execute( "load data local infile '#{RAILS_ROOT}/public/muds_variables.csv' into table muds_variables " + "fields terminated by ',' " + "lines terminated by '\n' " + "(variable_name, definition)") I've checked and re-checked the file path, and that's definitely where it lives, I've also tried it just using the file name without any of the path, and a few other combos, but I can't make it work :(. can anyone help me out with this? here's the error : Mysql::Error: File '/home/chris/rails_projects/muds/public/muds_variables.csv' not found (Errcode: 2): load data local infile '/home/chris/rails_projects/muds/public/muds_variables.csv' into table muds_variables fields terminated by ',' lines terminated by ' ' (variable_name, definition) -C

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• Extension method on type

  - by Karsten

  Hi Is there a way to create an extension method for an type ? I only seem to be able to create them for instances. public static class MyExtensions { public static string Test(this string s) { return "test"; } } public class Test { static void TestIt() { string.Test(); // won't compile string s = null; s.Test(); } }

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• How should I provide access to this custom DAL?

  - by Casey

  I'm writing a custom DAL (VB.NET) for an ordering system project. I'd like to explain how it is coded now, and receive some alternate ideas to make coding against the DAL easier/more readable. The DAL is part of an n-tier (not n-layer) application, where each tier is in it's own assembly/DLL. The DAL consists of several classes that have specific behavior. For instance, there is an Order class that is responsible for retrieving and saving orders. Most of the classes have only two methods, a "Get" and a "Save," with multiple overloads for each. These classes are marked as Friend and are only visible to the DAL (which is in it's own assembly). In most cases, the DAL returns what I will call a "Data Object." This object is a class that contains only data and validation, and is located in a common assembly that both the BLL and DAL can read. To provide public access to the DAL, I currently have a static (module) class that has many shared members. A simplified version looks something like this: Public Class DAL Private Sub New End Sub Public Shared Function GetOrder(OrderID as String) as OrderData Dim OrderGetter as New OrderClass Return OrderGetter.GetOrder(OrderID) End Function End Class Friend Class OrderClass Friend Function GetOrder(OrderID as string) as OrderData End Function End Class The BLL would call for an order like this: DAL.GetOrder("123456") As you can imagine, this gets cumbersome very quickly. I'm mainly interested in structuring access to the DAL so that Intellisense is very intuitive. As it stands now, there are too many methods/functions in the DAL class with similar names. One idea I had is to break down the DAL into nested classes: Public Class DAL Private Sub New End Sub Public Class Orders Private Sub New End Sub Public Shared Function Get(OrderID as string) as OrderData End Function End Class End Class So the BLL would call like this: DAL.Orders.Get("12345") This cleans it up a bit, but it leaves a lot of classes that only have references to other classes, which I don't like for some reason. Without resorting to passing DB specific instructions (like where clauses) from BLL to DAL, what is the best or most common practice for providing a single point of access for the DAL?

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• NullReferenceException when testing DefaultModelBinder.

  - by Byron Sommardahl

  I'm developing a project using BDD/TDD techniques and I'm trying my best to stay the course. A problem I just ran into is unit testing the DefaultModelBinder. I'm using mspec to write my tests. I have a class like this that I want to bind to: public class EmailMessageInput : IMessageInput { public object Recipient { get; set; } public string Body { get; set; } } Here's how I'm building my spec context. I'm building a fake form collection and stuffing it into a bindingContext object. public abstract class given_a_controller_with_valid_email_input : given_a_controller_context { Establish additional_context = () => { var form = new FormCollection { new NameValueCollection { { "EmailMessageInput.Recipient", "[email protected]"}, { "EmailMessageInput.Body", "Test body." } } }; _bindingContext = new ModelBindingContext { ModelName = "EmailMessageInput", ValueProvider = form }; _modelBinder = new DefaultModelBinder(); }; protected static ModelBindingContext _bindingContext; protected static DefaultModelBinder _modelBinder; } public abstract class given_a_controller_context { protected static MessageController _controller; Establish context = () => { _controller = new MessageController(); }; } Finally, my spec throws an null reference exception when I execute .BindModel() from inside one of my specs: Because of = () => { _model = _modelBinder.BindModel(_controller.ControllerContext, _bindingContext); }; Any clue what it could be? Feel free to ask me for more info, if needed. I might have taken something for granted.

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• ASP.NET MVC 2.0 Unused Model Property being called when posting a product to the server?

  - by Erx_VB.NExT.Coder

  i have my auto-generated linq to sql classes, and i extend this class using partial classing (instead of using inheritance), and i have properties that that i've put in later which are not part of the database model and should not be. these are things like "FinalPrice" and "DisplayFinalPrice" - in the dbase, there is only RetailPrice and WholesalePrice so FinalPrice etc are more like extensions of the dbase fields. when i submit the form with nothing filled in, "FinalPrice" gets called (the 'get' of the property) even tho i never ask for it to be, and even tho it is not needed. this happens before validation, so i don't even get the validation errors i would get. i've tried using and on the FinalPrice and FinalPriceDisplay properties - no go! why does this happen and how can i stop it from happening? is the modelstate just trying to validate everything so therefore it calls every item no matter what? for those interested, here is all the code... Partial Public Class tProduct 'Inherits tProduct Private Const CommissionMultiplier As Decimal = CDec(1.18) Private _FinalPrice As Decimal? Private _DisplayFinalPrice As String Private _DisplayNormalPrice As String Public Property CategoryComplete As Short <ScaffoldColumn(False)> Public ReadOnly Property FinalPrice As Decimal Get 'If RetailPrice IsNot Nothing OrElse WholesalePrice IsNot Nothing Then If _FinalPrice Is Nothing Then If RetailPrice IsNot Nothing Then _FinalPrice = RetailPrice Else _FinalPrice = WholesalePrice * CommissionMultiplier ' TODO: this should be rounded to the nearest 5th cent so prices don't look weird. End If Dim NormalPart = Decimal.Floor(_FinalPrice.Value) Dim DecimalPart = _FinalPrice.Value - NormalPart If DecimalPart = 0 OrElse DecimalPart = 0.5 Then Return _FinalPrice ElseIf DecimalPart > 0 AndAlso DecimalPart < 0.5 Then DecimalPart = 0.5 ' always rounded up to the nearest 50 cents. ElseIf DecimalPart > 0.5 AndAlso DecimalPart < 1 Then ' Only in this case round down if its about to be rounded up to a valeu like 20, 30 or 50 etc as we want most prices to end in 9. If NormalPart.ToString.LastChr.ToInt = 9 Then DecimalPart = 0.5 Else DecimalPart = 1 End If End If _FinalPrice = NormalPart + DecimalPart End If Return _FinalPrice 'End If End Get End Property <ScaffoldColumn(False)> Public ReadOnly Property DisplayFinalPrice As String Get If _DisplayFinalPrice.IsNullOrEmpty Then _DisplayFinalPrice = FormatCurrency(FinalPrice, 2, TriState.True) End If Return _DisplayFinalPrice End Get End Property Public ReadOnly Property DisplayNormalPrice As String Get If _DisplayNormalPrice.IsNullOrEmpty Then _DisplayNormalPrice = FormatCurrency(NormalPrice, 2, TriState.True) End If Return _DisplayNormalPrice End Get End Property Public ReadOnly Property DivID As String Get Return "pdiv" & ProductID End Get End Property End Class more... i get busted here, with a null reference exception telling me it should contain a value... Dim NormalPart = Decimal.Floor(_FinalPrice.Value)

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• Visitor and templated virtual methods

  - by Thomas Matthews

  In a typical implementation of the Visitor pattern, the class must account for all variations (descendants) of the base class. There are many instances where the same method content in the visitor is applied to the different methods. A templated virtual method would be ideal in this case, but for now, this is not allowed. So, can templated methods be used to resolve virtual methods of the parent class? Given (the foundation): struct Visitor_Base; // Forward declaration. struct Base { virtual accept_visitor(Visitor_Base& visitor) = 0; }; // More forward declarations struct Base_Int; struct Base_Long; struct Base_Short; struct Base_UInt; struct Base_ULong; struct Base_UShort; struct Visitor_Base { virtual void operator()(Base_Int& b) = 0; virtual void operator()(Base_Long& b) = 0; virtual void operator()(Base_Short& b) = 0; virtual void operator()(Base_UInt& b) = 0; virtual void operator()(Base_ULong& b) = 0; virtual void operator()(Base_UShort& b) = 0; }; struct Base_Int : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_Long : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_Short : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_UInt : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_ULong : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_UShort : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; Now that the foundation is laid, here is where the kicker comes in (templated methods): struct Visitor_Cout : public Visitor { template <class Receiver> void operator() (Receiver& r) { std::cout << "Visitor_Cout method not implemented.\n"; } }; Intentionally, Visitor_Cout does not contain the keyword virtual in the method declaration. All the other attributes of the method signatures match the parent declaration (or perhaps specification). In the big picture, this design allows developers to implement common visitation functionality that differs only by the type of the target object (the object receiving the visit). The implementation above is my suggestion for alerts when the derived visitor implementation hasn't implement an optional method. Is this legal by the C++ specification? (I don't trust when some says that it works with compiler XXX. This is a question against the general language.)

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• Qt - drag and drop with graphics view framework

  - by David Davidson

  I'm trying to make a simple draggable item using the graphics framework. Here's the code for what I did so far: Widget class: class Widget : public QWidget { Q_OBJECT public: Widget(QWidget *parent = 0); ~Widget(); }; Widget::Widget(QWidget *parent) : QWidget(parent) { DragScene *scene = new DragScene(); DragView *view = new DragView(); QHBoxLayout *layout = new QHBoxLayout(); DragItem *item = new DragItem(); view->setAcceptDrops(true); scene->addItem(item); view->setScene(scene); layout->addWidget(view); this->setLayout(layout); } Widget::~Widget() { } DragView class: class DragView : public QGraphicsView { public: DragView(QWidget *parent = 0); }; DragView::DragView(QWidget *parent) : QGraphicsView(parent) { setRenderHints(QPainter::Antialiasing); } DragScene class: class DragScene : public QGraphicsScene { public: DragScene(QObject* parent = 0); protected: void dragEnterEvent(QGraphicsSceneDragDropEvent *event); void dragMoveEvent(QGraphicsSceneDragDropEvent *event); void dragLeaveEvent(QGraphicsSceneDragDropEvent *event); void dropEvent(QGraphicsSceneDragDropEvent *event); }; DragScene::DragScene(QObject* parent) : QGraphicsScene(parent) { } void DragScene::dragEnterEvent(QGraphicsSceneDragDropEvent *event){ } void DragScene::dragMoveEvent(QGraphicsSceneDragDropEvent *event){ } void DragScene::dragLeaveEvent(QGraphicsSceneDragDropEvent *event){ } void DragScene::dropEvent(QGraphicsSceneDragDropEvent *event){ qDebug() << event->pos(); event->acceptProposedAction(); DragItem *item = new DragItem(); this->addItem(item); item->setPos(event->pos()); } DragItem class: class DragItem : public QGraphicsItem { public: DragItem(QGraphicsItem *parent = 0); QRectF boundingRect() const; void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0); protected: void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event); void mouseMoveEvent(QGraphicsSceneMouseEvent *event); void mousePressEvent(QGraphicsSceneMouseEvent *event); void mouseReleaseEvent(QGraphicsSceneMouseEvent *event); }; DragItem::DragItem(QGraphicsItem *parent) : QGraphicsItem(parent) { setFlag(QGraphicsItem::ItemIsMovable); } QRectF DragItem::boundingRect() const{ const QPointF *p0 = new QPointF(-10,-10); const QPointF *p1 = new QPointF(10,10); return QRectF(*p0,*p1); } void DragItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget){ if(painter == 0) painter = new QPainter(); painter->drawEllipse(QPoint(0,0),10,10); } void DragItem::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event){ } void DragItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event){ } void DragItem::mousePressEvent(QGraphicsSceneMouseEvent *event){ QMimeData* mime = new QMimeData(); QDrag* drag = new QDrag(event->widget()); drag->setMimeData(mime); drag->exec(); } void DragItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *event){ } main.cpp instantiates a Widget and shows it. When I try to drag the circle, the app just creates another circle over the original one, regardless of where I release the drag. qDebug() in DragScene's dropEvent() shows QPointF(0,0) everytime the drag ends. I'm having a hard time trying to understand exactly what I have to do, which classes I should subclass, which methods needs to be overriden, to make this work. The documentation on this isn't very detailed. I'd like to know how to make this work, and if there's some other, more comprehensive resource to learn about the graphics view framework, besides the official documentation (which is excellent btw, but it would be great if there was a more detailed treatise on the subject). EDIT: Following badgerr's advice, I replaced item-pos() in DragScene::dropEvent() with item-scenePos(), now the drop event creates a new circle in the drop site, which is more or less what I wanted. But the original circle is still in place, and while the drag is in progress, the item doesn't follow the mouse cursor. The QGraphicsSceneDragDropEvent documentation says that pos() should return the cursor position in relation to the view that sent the event, which, unless I got it wrong, shouldn't be (0,0) all the time. Weird. I've read in a forum post that you can use QDrag::setPixMap() to show something during the drag, and in examples I've seen pictures being set as pixmaps, but how do I make the pixmap just like the graphics item I'm supposed to be dragging?

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• JPA @ManyToOne and composite PK

  - by Fleuri F

  Good Morning, I am working on project using JPA. I need to use a @ManyToOne mapping on a class that has three primary keys. You can find the errors and the classes after this. If anyone has an idea! Thanks in advance! FF javax.persistence.PersistenceException: No Persistence provider for EntityManager named JTA_pacePersistence: Provider named oracle.toplink.essentials.PersistenceProvider threw unexpected exception at create EntityManagerFactory: javax.persistence.PersistenceException javax.persistence.PersistenceException: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [JTA_pacePersistence] failed. Internal Exception: Exception [TOPLINK-7220] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: The @JoinColumns on the annotated element [private java.util.Set isd.pacepersistence.common.Action.permissions] from the entity class [class isd.pacepersistence.common.Action] is incomplete. When the source entity class uses a composite primary key, a @JoinColumn must be specified for each join column using the @JoinColumns. Both the name and the referenceColumnName elements must be specified in each such @JoinColumn. at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:643) at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:196) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:110) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at isd.pacepersistence.common.DataMapper.(Unknown Source) at isd.pacepersistence.server.MainServlet.getDebugCase(Unknown Source) at isd.pacepersistence.server.MainServlet.doGet(Unknown Source) at javax.servlet.http.HttpServlet.service(HttpServlet.java:718) at javax.servlet.http.HttpServlet.service(HttpServlet.java:831) at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:411) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:290) at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:271) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:202) There is the source code of my classes : Action : @Entity @Table(name="action") public class Action { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private int num; @ManyToOne(cascade= { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH }) @JoinColumn(name="domain_num") private Domain domain; private String name; private String description; @OneToMany @JoinTable(name="permission", joinColumns= { @JoinColumn(name="action_num", referencedColumnName="action_num", nullable=false, updatable=false) }, inverseJoinColumns= { @JoinColumn(name="num") }) private Set<Permission> permissions; public Action() { } Permission : @SuppressWarnings("serial") @Entity @Table(name="permission") public class Permission implements Serializable { @EmbeddedId private PermissionPK primaryKey; @ManyToOne @JoinColumn(name="action_num", insertable=false, updatable=false) private Action action; @ManyToOne @JoinColumn(name="entity_num", insertable=false, updatable=false) private isd.pacepersistence.common.Entity entity; @ManyToOne @JoinColumn(name="class_num", insertable=false, updatable=false) private Clazz clazz; private String kondition; public Permission() { } PermissionPK : @SuppressWarnings("serial") @Entity @Table(name="permission") public class Permission implements Serializable { @EmbeddedId private PermissionPK primaryKey; @ManyToOne @JoinColumn(name="action_num", insertable=false, updatable=false) private Action action; @ManyToOne @JoinColumn(name="entity_num", insertable=false, updatable=false) private isd.pacepersistence.common.Entity entity; @ManyToOne @JoinColumn(name="class_num", insertable=false, updatable=false) private Clazz clazz; private String kondition; public Permission() { }

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• Using an array as parameter to a class.

  - by Gabriel A. Zorrilla

  I have created an array Man: public main blah blah{ man = man[10]; } Man has fields such as Man.name; Man.age; ... In Man class, there is a OnClick method that opens a new window showing its name and age. public Man(){ Onclick(){ InfoWindow showinfo = new InfoWindow(this.getid()) // If this is Man[2] the id would be 2. } And in InfoWindow class: public class InfoWindow extends JFrame{ public InfoWindow(Man selectedMan){ setSize(300, 200); JLabel info = new JLabel(selectedMan.getname()); add(info); info.setVisible(true); } } Basically, that's wanna acomplish (show in pseudocode), pass a Man[i] into a class that when a window is created, shows the info related to that man. This is how i'm actualy trying to implement it but it's not working, i'm pretty sure there is a misconception from me in some part. Any help?

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• how to store JSON into POJO using Jackson

  - by user2963680

  I am developing a module where i am using rest service to get data. i am not getting how to store JSON using Jackson and store it which has Queryparam also. Any help is really appreciated as I am new to this.I am trying to do server side filtering in extjs infinte grid which is sending the below request to rest service. when the page load first time, it sends http://myhost/mycontext/rest/populateGrid?_dc=9999999999999&page=1&start=0&limit=500 when you select filter on name and place, it sends http://myhost/mycontext/rest/populateGrid?_dc=9999999999999&filter=[{"type":"string","value":"Tom","field":"name"},{"type":"string","value":"London","field":"Location"}]&page=1&start=0&limit=500 I am trying to save this in POJO and then sending this to database to retrieve data. For this on rest side i have written something like this @Provider @Path("/rest") public interface restAccessPoint { @GET @Path("/populateGrid") @Produces({MediaType.APPLICATION_JSON}) public Response getallGridData(FilterJsonToJava filterparam,@QueryParam("page") String page,@QueryParam("start") String start,@QueryParam("limit") String limit); } public class FilterJsonToJava { @JsonProperty(value ="filter") private List<Filter> data; .. getter and setter below } public class Filter { @JsonProperty("type") private String type; @JsonProperty("value") private String value; @JsonProperty("field") private String field; ...getter and setters below } I am getting the below error The following warnings have been detected with resource and/or provider classes: WARNING: A HTTP GET method, public abstract javax.ws.rs.core.Response com.xx.xx.xx.xxxxx (com.xx.xx.xx.xx.json.FilterJsonToJava ,java.lang.String,java.lang.String,java.lang.String), should not consume any entity. com.xx.xx.xx.xx.json.FilterJsonToJava, and Java type class com.xx.xx.xx.FilterJsonToJava, and MIME media type application/octet-stream was not found [11/6/13 17:46:54:065] 0000001c ContainerRequ E The registered message body readers compatible with the MIME media type are: application/octet-stream com.sun.jersey.core.impl.provider.entity.ByteArrayProvider com.sun.jersey.core.impl.provider.entity.FileProvider com.sun.jersey.core.impl.provider.entity.InputStreamProvider com.sun.jersey.core.impl.provider.entity.DataSourceProvider com.sun.jersey.core.impl.provider.entity.RenderedImageProvider */* -> com.sun.jersey.core.impl.provider.entity.FormProvider ...

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• How do I repopulate the view model in ASP.NET MVC 2 after a validation error?

  - by Keltex

  I'm using ASP.NET MVC 2 and here's the issue. My View Model looks something like this. It includes some fields which are edited by the user and others which are used for display purposes. Here's a simple version public class MyModel { public decimal Price { get; set; } // for view purpose only [Required(ErrorMessage="Name Required")] public string Name { get; set; } } The controller looks something like this: public ActionResult Start(MyModel rec) { if (ModelState.IsValid) { Repository.SaveModel(rec); return RedirectToAction("NextPage"); } else { // validation error return View(rec); } } The issue is when there's a validation error and I call View(rec), I'm not sure the best way to populate my view model with the values that are displayed only. The old way of doing it, where I pass in a form collection, I would do something like this: public ActionResult Start(FormCollection collection) { var rec = Repository.LoadModel(); UpdateModel(rec); if (ModelState.IsValid) { Repository.SaveModel(rec); return RedirectToAction("NextPage"); } else { // validation error return View(rec); } } But doing this, I get an error on UpdateModel(rec): The model of type 'MyModel' could not be updated. Any ideas?

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• Spring MVC configuration problems

  - by Smek

  i have some problems with configuring Spring MVC. I made a maven multi module project with the following modules: /api /domain /repositories /webapp I like to share the domain and the repositories between the api and the webapp (both web projects). First i want to configure the webapp to use the repositories module so i added the dependencies in the xml file like this: <dependency> <groupId>${project.groupId}</groupId> <artifactId>domain</artifactId> <version>1.0-SNAPSHOT</version> </dependency> <dependency> <groupId>${project.groupId}</groupId> <artifactId>repositories</artifactId> <version>1.0-SNAPSHOT</version> </dependency> And my controller in the webapp module looks like this: package com.mywebapp.webapp; import com.mywebapp.domain.Person; import com.mywebapp.repositories.services.PersonService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.stereotype.Controller; import org.springframework.ui.ModelMap; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; @Controller @RequestMapping("/") @Configuration @ComponentScan("com.mywebapp.repositories") public class PersonController { @Autowired PersonService personservice; @RequestMapping(method = RequestMethod.GET) public String printWelcome(ModelMap model) { Person p = new Person(); p.age = 23; p.firstName = "John"; p.lastName = "Doe"; personservice.createNewPerson(p); model.addAttribute("message", "Hello world!"); return "index"; } } In my webapp module i try to load configuration files in my web.xml like this: <context-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:/META-INF/persistence-context.xml, classpath:/META-INF/service-context.xml</param-value> </context-param> These files cannot be found so i get the following error: org.springframework.beans.factory.BeanDefinitionStoreException: IOException parsing XML document from class path resource [META-INF/persistence-context.xml]; nested exception is java.io.FileNotFoundException: class path resource [META-INF/persistence-context.xml] cannot be opened because it does not exist These files are in the repositories module so my first question is how can i make Spring to find these files? I also have trouble Autowiring the PersonService to my Controller class did i forget to configure something in my XML? Here is the error message: [INFO] [talledLocalContainer] SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener [INFO] [talledLocalContainer] org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'personServiceImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.mywebapp.repositories.repository.PersonRepository com.mywebapp.repositories.services.PersonServiceImpl.personRepository; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [com.mywebapp.repositories.repository.PersonRepository] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} PersonServiceImple.java: package com.mywebapp.repositories.services; import com.mywebapp.domain.Person; import com.mywebapp.repositories.repository.PersonRepository; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.data.mongodb.core.MongoTemplate; import org.springframework.stereotype.Service; @Service public class PersonServiceImpl implements PersonService{ @Autowired public PersonRepository personRepository; @Autowired public MongoTemplate personTemplate; @Override public Person createNewPerson(Person person) { return personRepository.save(person); } } PersonService.java package com.mywebapp.repositories.services; import com.mywebapp.domain.Person; public interface PersonService { Person createNewPerson(Person person); } PersonRepository.java: package com.mywebapp.repositories.repository; import com.mywebapp.domain.Person; import org.springframework.data.mongodb.repository.MongoRepository; import org.springframework.stereotype.Repository; import java.math.BigInteger; @Repository public interface PersonRepository extends MongoRepository<Person, BigInteger> { } persistance-context.xml <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:mongo="http://www.springframework.org/schema/data/mongo" xsi:schemaLocation= "http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/data/mongo http://www.springframework.org/schema/data/mongo/spring-mongo-1.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <context:property-placeholder location="classpath:mongo.properties"/> <mongo:mongo host="${mongo.host}" port="${mongo.port}" id="mongo"> <mongo:options connections-per-host="${mongo.connectionsPerHost}" threads-allowed-to-block-for-connection-multiplier="${mongo.threadsAllowedToBlockForConnectionMultiplier}" connect-timeout="${mongo.connectTimeout}" max-wait-time="${mongo.maxWaitTime}" auto-connect-retry="${mongo.autoConnectRetry}" socket-keep-alive="${mongo.socketKeepAlive}" socket-timeout="${mongo.socketTimeout}" slave-ok="${mongo.slaveOk}" write-number="1" write-timeout="0" write-fsync="true"/> </mongo:mongo> <mongo:db-factory dbname="person" mongo-ref="mongo" id="mongoDbFactory"/> <bean id="personTemplate" name="personTemplate" class="org.springframework.data.mongodb.core.MongoTemplate"> <constructor-arg name="mongoDbFactory" ref="mongoDbFactory"/> </bean> <mongo:repositories base-package="com.mywebapp.repositories.repository" mongo-template-ref="personTemplate"> <mongo:repository id="personRepository" repository-impl-postfix="PersonRepository" mongo-template-ref="personTemplate" create-query-indexes="true"/> </mongo:repositories> Thanks

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• Dynamic Overlays slowing down Google Maps (Android 2.1) on Nexus One

  - by Soumya Simanta

  Hi, I'm trying to create a dynamic ItemizedOverylay (please see the code below) on Google Maps (Android 2.1) on a Nexus One. In my Activity (that extends MapActivity) I'm creating a data thread that is receiving data from the network. A 'handler' is used to communicate the data from the receiving thread to map activity. This data contains the locations (lat, lon) of the markers that I want to overlay on my map. The location of each marker is dynamic (i.e., it changes every time I receive new data from the network.) refreshItems(ArrayList<OverlayItem> newItems) method in invoked inside the handleMessage() of the handler. There are around 11 markers in the ArrayList that is passed to refreshItems I can see the markers overlayed on the map. However, I've two issues: The old markers are not removed from the map. After a while I see a trail of markers. The map doesn't respond to any touch commands. I cannot move the map or zoom in or zoom out. After a while I see a system warning that my app is not responding message. Any idea what's wrong here ? Thanks. public class MyItemizedOverlay extends ItemizedOverlay { private ArrayList<OverlayItem> overlayItems; public CoTItemizedOverlay(Drawable defaultMarker) { super(boundCenter(defaultMarker)); overlayItems = new ArrayList<OverlayItem>(); populate(); } public void addNewItem(GeoPoint location, String markerText, String snippet) { overlayItems.add(new OverlayItem(location, markerText, snippet)); populate(); } public void removeItem(int index) { overlayItems.remove(index); populate(); } public void refreshItems(ArrayList<OverlayItem> newItems) { // remove all existing items for (int i = 0; i < cotoverlayItems.size(); i++) { overlayItems.remove(i); } // copy all the times if (newItems != null && cotoverlayItems.size() == 0) { overlayItems.addAll(newItems); } populate(); } @Override protected OverlayItem createItem(int index) { return overlayItems.get(index); } @Override public int size() { return overlayItems.size(); } }

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• MVVM: how to set the datacontext of a user control

  - by EVA

  Hi, I'm writing an application in WPF, using the MVVm toolkit and have problems with hooking up the viewmodel and view. The model is created with ado.net entity framework. The viewmodel: public class CustomerViewModel { private Models.Customer customer; //constructor private ObservableCollection<Models.Customer> _customer = new ObservableCollection<Models.Customer>(); public ObservableCollection<Models.Customer> AllCustomers { get { return _customer; } } private Models.Customer _selectedItem; public Models.Customer SelectedItem { get { return _selectedItem; } } public void LoadCustomers() { List<Models.Customer> list = DataAccessLayer.getcustomers(); foreach (Models.Customer customer in list) { this._customer.Add(customer); } } } And the view (no code behind at the moment): <UserControl x:Class="Customers.Customer" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" mc:Ignorable="d" xmlns:vm ="clr-namespace:Customers.ViewModels" d:DesignHeight="300" d:DesignWidth="300" xmlns:toolkit="http://schemas.microsoft.com/wpf/2008/toolkit" > <Grid> <toolkit:DataGrid ItemsSource="{Binding AllCustomers}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}" AutoGenerateColumns="True"> </toolkit:DataGrid> <toolkit:DataGrid ItemsSource="{Binding SelectedItem.Orders}"> </toolkit:DataGrid> </Grid> </UserControl> And dataaccesslayer class: class DataAccessLayer { public List<Customer> customers = new List<Customer>(); public static List<Customer> getcustomers() { entities db = new entities(); var customers = from c in db.Customer.Include("Orders") select c; return customers.ToList(); } } The problem is that no data is displayed simply because the data context is not set. I tried to do it in a code-behind but is did not work. I would prefer to do it in a xaml file anyway. Another problem is with the SelectedItem binding - the code is never used. Thanks for help! Regards, EV.

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