Silverlight custom control ToolTip not showing up each time

In a Silverlight application I have a custom control with a number of custom properties. In the declaration class of the custom control additionally to defining its properties as dependency properties, I define showing a ToolTip:

public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();
        Border bordercntr = base.GetTemplateChild("PART_SBorder") as Border;
        bordercntr.MouseEnter += new MouseEventHandler(bordercntr_MouseEnter);
        bordercntr.MouseLeave += new MouseEventHandler(bordercntr_MouseLeave);

    }

    private void bordercntr_MouseEnter(object sender, MouseEventArgs e)
    {
       string _sno = this.S开发者_如何学ComeProperty.ToString();

       ToolTipService.SetToolTip(this, "Some text " + _sno);
       VisualStateManager.GoToState(this, "Hovered",false);                            
    }

The problem is, that a ToolTip pops up not the first time mouse points to a custom control, but only after the second time. After I reload page this happens again: the first time I hover over a control nothing is shown up and then from the second time and further on the ToolTip pops up again. (not always in a stable way, I mean not 100% each time mouse hovers).

What could prevent the ToolTip from showing up in a stable manner each time a mouse hovers over control and starting showing up from the very first time of hovering it after reloading the page?

Set the ToolTip in the setter for SomeProperty The ToolTip you define in the ToolTipService will behave like a normal ToolTip and only appear when the mouse is over the control. You shouldn't need to handle the MouseEnter and MouseLeave events at all.