Question

I am trying to use asynchronous calls to save a database and I have realised my understanding of how things work may be incorrect. I have done a number of google searches but it hasn’t helped to reduce my confusion

What I have is similar to the following:

private delegate bool MyDelegate();

private void ExportButton_Click(object sender, EventArgs e)
{
    // Disable button
    exportButton.Enabled = false;

    MyDelegate deleg = ExportDatabase;

    // Begin the export
    deleg.BeginInvoke(ExportDatabaseCallback, null);
}

public bool ExportDatabase()
{
    // Do Stuff
    return true;
}

private void ExportDatabaseCallback(IAsyncResult ar)
{
    // Enable button
    Invoke((MethodInvoker)delegate { exportButton.Enabled = true; });

    MessageBox.Show("Exporting Database complete");
}

Now, looking at other pages seems to indicate in my BeginInvoke I should do this as: deleg.BeginInvoke(new AsyncCallback(ExportDatabaseCallback), null); but what I have works, so am I doing something wrong here?

the other thing is that I believe in my callback I am supposed to call EndInvoke() as other stackoverflow questions state it is not optional. But then in other places it seems it is? But most comments I can find are from 2009 and I don’t know if things have changed since then. Is this the only way to get the bool from the ExportDatabase?

Answer 1

 new AsyncCallback(ExportDatabaseCallback)

is just the old, longer way to create a delegate. Your code does exactly the same.

And EndInvoke() is sometimes optional but you don’t want to know when and when not. Just call it, and you’re always right.