static box at design time

[randalthor100]

this is probably a stupid question....but how do you make an object ... say a combobox static at design time? (in the design tab)

i must be missing something but i can't see any option for it

J

[DevGrp]

You have to do it in the code. When you add the combobox to your form, look where its declared and just add the static keyword to it.

[CornedBee]

Would that even work? What's the use of it?

[randalthor100]

DevGrp: thanks.....i was looking for a way around having to impliment it in the code....just being lazy i guess...oh well

bee: i need to be able to manipulate the selectedItem property from within static methods and since it was created at design time i can't reference the instance ... at least i don't think i can

cheers for the help and the speedy replies

J

[CornedBee]

Sounds like you should rethink your code design. Why do you need to reference it from static methods?

[randalthor100]

well.......

I have a browser, pretty much exactly the same as ie, i have a separate thread that runs to evaluate the "mood" of a document that is being displayed by the browser. This has to be on a different thread because depending ong the machine learning technique that the user has chose, it can take a while to learn anything, and the desire was to have a browser that didn't interrupt the user with long delays. Once the machine learning techniques have made a desicion it calls a method in my original file to tell the combobox to change to reflect this discovery. It also sets a lable to show the percentage certanty that it has chosen the right mood.

There is a lot more to it....but this is what i think you want to know

If there's an easier way to reference methods across files and threads i'd love to know about it

J

[Scott Penner]

There are a few things you could do.

You could pass the mood class a reference to the combo box after it has been created. But, it might be more appropriate to fire an event from the mood class that the combo box class consumes.

I believe this should work accross thread as long as you synchronize access to the combo box.

[CornedBee]

Sounds very interesting.

But take heed of this remark in the documentation of the Control class:

Note There are four methods on a control that are safe to call from any thread: Invoke, BeginInvoke, EndInvoke, and CreateGraphics. For all other method calls, you should use one of the invoke methods to marshal the call to the control's thread.

[Scott Penner]

This should work.
The worker class has a single method that takes a reference to a textbox control and starts a worker thread to pause for 5 seconds then append text to the text box.
The code in the form simply creates the class and passes a reference to a created textbox control into the DoWork method.

Worker Class

public delegate void UpdateText(string NewText);

public class Worker
{
    public Worker()
    {
        // nothing to do
    }

    public void DoWork(System.Windows.Forms.TextBox ReferencedBox)
    {
        // Put the work in the thread pool queue
        ThreadPool.QueueUserWorkItem(new WaitCallback(this.DoWorkAsync),ReferencedBox);
    }

    private void DoWorkAsync(object state)
    {
        // Sleep for 5 seconds
        Thread.Sleep(5000);

        // Put in catch block in case object is not textbox type
        try
        {
            TextBox TempText = (TextBox)state;

            // Invoke the append text method via the updatetext delegate
            TempText.Invoke(new UpdateText(TempText.AppendText),new object[] {DateTime.Now.ToShortDateString()});
        }
        catch{}

    }
}
} 

In Form:

private System.Windows.Forms.TextBox textThreadTest;
private Worker localWorker;

public ControlMain()
{
...
      // Instantiate the worker class and pass a reference to the
      // text box into the DoWork method
    localWorker = new Worker();
    localWorker.DoWork(this.textThreadTest);
}