Question

I’m new to WPF (and computer science in general) and I was given a small project from my boss where there are 5 tabs, each that go to a different site. After logging in, the user is directed to the website of the 1st tab. In the background, the 4 other tabs should be loading in the background.

Each has the following name: “tabItem1”, “tabItem2”, “tabItem3”, “tabItem4” up to “tabItem5”
Inside each there is a up to “webBrowser5”.

I think that I have to use threading to load the pages in the background, but I’m not sure how to implement it. I tried creating 4 different threads in the MainWindow such as:

public MainWindow()
{
     InitializeComponent();

     Thread thread1 = new Thread(Update1);
     thread1.SetApartmentState(ApartmentState.STA);
     thread1.Start();

     Thread thread2 = new Thread(Update2);
     thread2.SetApartmentState(ApartmentState.STA);
     thread2.Start();

     Thread thread3 = new Thread(Update3);
     thread3.SetApartmentState(ApartmentState.STA);
     thread3.Start();

     Thread thread4 = new Thread(Update4);
     thread4.SetApartmentState(ApartmentState.STA);
     thread4.Start();
}

private void Update1()
    {
      this.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
          (ThreadStart)delegate()
              {
                tabItem2.Focus();
              }
          );
    }

private void Update2()
    {
      this.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
          (ThreadStart)delegate()
              {
                tabItem3.Focus();
              }
          );
    }

//...Goes up to Update4

This seems to only focus on the last thread and also it doesn’t do it the background. I appreciate any guidance and help. Thanks!

Answer 1

That IS what the dispatcher is doing, operating on the main thread. You told the main thread to set focus because the object is on the main thread.

The problem:

The answer lies in why you must do this. You cannot operate on a windows control in any other thread than the thread it was created on. You also can’t create a control in one thread, and set it as a child of a control in another thread.

What this means to you… is that what your boss asked you to do can’t be done. The only thing you can do in the background is calculate algorithms. At best, you’ll be able to load data, and operate on data, and interpret data, but if you want to have that data be displayed in, or converted into, windows controls, you must do that on the main thread.

The only solution:

However, you can have multiple UIThreads. Which means you can create multiple Windows. So, the must-do alternative is to create windows on separate threads for each tab content, then host the thread-windows on each tab.

Threading windows

Host process window

Cross thread hosting