WPF waiting message while rendering a template - wpf

Question

In my legacy project I've a treeview and an OnClick event binded on treeview leafs. Basically each time I choose a leaf, I get the node type and I apply a template into a control such:
gridDati.Template = Resources["tmplBit"] as ControlTemplate;
The "tmplBit" is a DataTemplate with several columns. All works fine but sometimes when I have 20 columns and 30/40 records, it takes time (4/5 sec) while applying the chosen template.
I would like to show a waiting message, or something like that but I cannot find how. I've already a window that show a waiting message, I tried to use as:
var aboutBox = new winWaitingMessage(Global.LM.T("#_3261_Inizio export"));
aboutBox.Show();
// Template?
gridDati.Template = Resources["tmplBit"] as ControlTemplate;
aboutBox.Close();
but the box is closed immediately, so I cannot find an event that tell me when the template is applied and rendered. Any hints?

Answer 1

you can use task
[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern IntPtr FindWindow(IntPtr hwnd, string title);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern int PostMessage(IntPtr hwnd, int msg, uint wParam, uint lParam);
public const int WM_CLOSE = 0x10;
public const int WM_KEYDOWN = 0x0100;
public const int WM_KEYUP = 0x0101;
public const int VK_RETURN = 0x0D;
private void Button_Click(object sender, RoutedEventArgs e)
{
Task task1 = new Task(() =>
{
gridDati.Template = Resources["tmplBit"] as ControlTemplate;
});
task1.Start();
Task cwt = task1.ContinueWith(t=>
{
FindAndKillWindow("Warning");
});
MessageBox.Show("Waiting...", "Warning");
}
private static void FindAndKillWindow(string title)
{
IntPtr ptr = FindWindow(IntPtr.Zero, title);
if (ptr != IntPtr.Zero)
{
int ret = PostMessage(ptr, WM_CLOSE, 0, 0);
ptr = FindWindow(IntPtr.Zero, title);
if (ptr != IntPtr.Zero)
{
PostMessage(ptr, WM_KEYDOWN, VK_RETURN, 0);
PostMessage(ptr, WM_KEYUP, VK_RETURN, 0);
}
}
}

Answer 2

The framework provides no such event but you could handle the Loaded event for an element in the template and close the window when this event occurs, e.g.:
gridDati.Template = Resources["tmplBit"] as ControlTemplate;
gridDati.ApplyTemplate();
FrameworkElement fe = gridDati.Template.FindName("YourElement", gridDati) as FrameworkElement;
if (fe == null)
{
aboutBox.Close();
}
else
{
void Fe_Loaded(object sender, RoutedEventArgs e)
{
aboutBox.Close();
fe.Loaded -= Fe_Loaded;
}
fe.Loaded += Fe_Loaded;
}
XAML:
<ControlTemplate x:Key="tmplBit">
...
<Button x:Name="YourElement" ... />
Edit: If you don't want to or can't use a local function for whatever reason, you could use a lambda expression to achieve the same thing:
...
else
{
RoutedEventHandler loadedHandler = null;
loadedHandler = (s, e) =>
{
aboutBox.Close();
fe.Loaded -= loadedHandler;
};
fe.Loaded += loadedHandler;
}