Question

I really do not understand how is this error happening at this code. Please check the code yourself

    void dispatcherTimer_Tick(object sender, EventArgs e)
{
    string srUrl = lstLocalIndex[irLocalIndex] + lstMainIndex[irMainIndex].Replace("0;","");

    Task.Factory.StartNew(() =>
    {
        startNewWindow(srUrl);
    });

}


    void startNewWindow(string srUrl)
{
    NewWindowThread<TitleWindow, string>(c => new TitleWindow(c), srUrl);
}

Now this code is where the error happening. I will also attach screenshot

        private void NewWindowThread<T, P>(Func<P, T> constructor, P param) where T : Window
    {
        Thread thread = new Thread(() =>
        {
            T w = constructor(param);
            w.Show();
            w.Closed += (sender, e) => w.Dispatcher.InvokeShutdown();
            try
            {
                System.Windows.Threading.Dispatcher.Run();
            }
            catch
            {

            }
        });
        thread.SetApartmentState(ApartmentState.STA);
        try
        {
            thread.Start();
        }
        catch
        {

        }
    }

This error causes whole software throw error and stop working even though i am calling them in new thread 🙁

This line throwing error System.Windows.Threading.Dispatcher.Run();

Please check also screenshot

C# 4.0 WPF

Answer 1

You are using a lambda as a thread function. This lambda is called on a new thread. At the
moment the thread is actually created, it will look for the argument you supply, which is a local variable srUrl, but by the time this happens your function (dispatcherTimer_Tick) has already exited, so srUrl will be in a part of the stack that is no longer properly defined (hence the access violation). The easy fix is to define a variable in the class and stuff the srLoc there quickly. A more proper solution is to actually pass the srLoc as argument:

() =>
{
    startNewWindow(srUrl);
}

becomes

(Action<string>){x => {startNewWindow(x);},
            new object[] {srUrl}

Now the function reference and a proper copy of the string are saved for the function call, and it doesn’t matter that the original srUrl is out of scope by the time the thread kicks in. I’m not sure whether the task factory allows the argument array to be passed. dispatchers normally have an overload for this, so maybe you want to let your window take care of this.

Now you actually do this a few times, so you may need to wrap the arguments each time they are passed.