Question

I have a UserControl(CardGUI) that I created for my WPF canvas, and I implemented MouseEvents on the UserControl like the ones below. Thing is when I drag the UserControl from the toolbox onto the canvas, it works just fine, but when I try to add a new control, CardGUI card = new CardGUI(); in my MainForm, I can no longer move the control, and I can’t figure out why this is.

I tried debugging but the events still get triggered when I click on the newly added control, yet I cannot move it.

public void UserControl_MouseLeftButtonDown(object sender, 
                                            MouseButtonEventArgs e)
{
    if (!inDrag)
    {
        anchorPoint = e.GetPosition(null);
        CaptureMouse();
        inDrag = true;
        e.Handled = true;
    }
}

public void UserControl_MouseMove(object sender, MouseEventArgs e)
{
    if (inDrag)
    {
        currentPoint = e.GetPosition(null);       
        Canvas.SetLeft(this, 
                       Canvas.GetLeft(this) + 
                           (currentPoint.X - anchorPoint.X));
        Canvas.SetTop(this, 
                      Canvas.GetTop(this) + 
                         (currentPoint.Y - anchorPoint.Y));
        anchorPoint = currentPoint;
        e.Handled = true;
    }
}

public void UserControl_MouseLeftButtonUp(object sender, 
                                          MouseButtonEventArgs e)
{
    if (inDrag)
    {
        ReleaseMouseCapture();
        inDrag = false;
        e.Handled = true;
    }
}

I add the control to my mainform like:

        this.deckCard = new CardGUI();            
        this.deckCard.Margin = new Thickness(xDeckCoord, yDeckCoord, 0, 0);
        this.main.Children.Add(this.deckCard);
        this.deckCard.IsHitTestVisible = true;
        this.deckCard.AllowDrop = true;

I figure it might be that since the method adding the control only gets called once, the location doesnt really update eventhough the event is triggered. I didn’t have that problem if I dragged the control from the ToolBox.

Answer 1

You are adding it to a Canvas, but not setting any position or size

Try adding:

this.main.SetLeft(deckCard, 0);
this.main.SetTop(deckCard, 0);

Or use a Grid instead if you want stuff to auto stretch to the available size (which your use of Margin seems to infer)