如何在工作线程中从UI线程中获取变量？

Question

I'm making slow progress on a simple application I'm making: it creates a request, fills out the headers and fetches a webpage for me. I figured out that in order to update the UI (after a button has been pressed) I must use dispatcher like so:

Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Send, new delegate_onearg_s(UpdateStatus), "Sending Request...");

In this case I have an UpdateStatus(string message) which sets my label_Status = message;

So far so good. Now I want it to take input from a textbox first and then turn it into a URL that is used later to create the request, but how do I do that? I've tried this:

string url = Convert.ToString(Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Send, new delegate_string_get(GetInput)));

GetInput() in this case simply does return textBox.Text; That doesn't really work - it returns some generic thing that's related to the dispatcher.

How can I get a variable from a textbox in the UI thread and get it in the working thread with the dispatcher?

Merci beacoup :)

PS. There's a very high probability I don't know what I'm doing. Just keep that in mind when answering.

Answer 1

You're on the right track, but you need to use Invoke , not BeginInvoke . BeginInvoke executes the delegate asynchronously on the dispatcher thread, but you need to get the result synchronously.

string url = (string)Dispatcher.Invoke(new Func<string>(GetInput));

Answer 2

before starting the thread, declare a string variable and assign to it the value from textBox then use that variable in your GetInput method.

string myVal = myTextBox.Text;

... use it in your GetInput.