private void BtnImport_Click(object sender, RoutedEventArgs e)
{
if (a == null)
{
//Instantiate the object and call the Open() method
a = new AddScreen("Trans");
a.Show();
//Add a event handler to set null our window object when it will be closed
a.Closed += new EventHandler(AddScreen_Closed);
}
//If the window was created and your window isn't active
//we call the method Activate to call the specific window to front
else if (a != null && !a.IsActive)
{
a.Activate();
}
a.DataChanged += AddScreen_DataChanged;
a.Show();
}
void AddScreen_Closed(object sender, EventArgs e)
{
a = null;
}