在backgroundworker中访问父窗口表单

Question

I have an extended method for messagebox.Show() , which uses IWin32Window of the parent winform to center the MessageBox on it.

However, I can't seem to understand how can we possibly use this same extension method to pop-up MessageBox on the main/parent winform from within BackgroundWorker .

The extension method is something like this:

MessageBoxExTn.Show(IWin32Window parentForm, string MsgText, string Caption, MessageBoxButtons);

I mean, I want to call this method from BackgroundWorker's DoWork event with threadsafe access to the parent/main winform.

Answer 1

You can add another method on your Main Form and do something like this

public void ShowMessage(string cap,string message)
    {
        if (this.InvokeRequired)
        {
            Action<string, string> action = ShowMessage;
            this.Invoke(action, new object[] {cap, message});
            return;
        }

       MessageBoxExTn.Show(IWin32Window parentForm, string MsgText, string Caption, MessageBoxButtons);
    }

please take a look at Control.InvokeRequired to understand more thread-safe in windows form

call your code

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
           ShowMessage(); 
        }

Answer 2

You could use event in this case and fire event when you want to show the message box. Now in your parent/main form handle this event and show the message box. This way you can achieve this.

Answer 3

You need to leverage the BackgroundWorker event ProgressChanged . This will do the thread switching for you. So imagine something like this:

private void backgroundWorker1_ProgressChanged(object sender,
    ProgressChangedEventArgs e)
{
    MessageBoxExTn.Show(parentForm,
        e.UserState as string,
        someCaption,
        MessageBoxButtons.OK);
}

and that's called like this:

backgroundWorker1.ReportProgress(1, "The message you want displayed.");