Question

If I use this to pass a string from my mainwindow to my customcontrol, how would I then capture it in my custom control?

    private void btnGeneral_Click(object sender, RoutedEventArgs e)
    {
        string myText = (string)Application.Current.Properties[textBox1.Text];
    }

Answer 1

Thats how you do it:

//To Set:    
App.Current.Properties["TextBoxString"] = textBox1.Text;
//To Get:
string myProperty = (string) App.Current.Properties["TextBoxString"];

Check out this article for Accessing the Application object in a WPF application