How to set toolTip of controls below the controls in wpf?

Question

Hi All,

I am working on one app in which I want to set tooltip for my radio button when window loaded. For that I wrote below code

Xaml Code:

<RadioButton Name="rb" Content="Check All">
                <RadioButton.ToolTip>
                    <ToolTip Name="tip" Content="Please Select the radio button"/>
                </RadioButton.ToolTip>
 </RadioButton>

CodeBehind Code:

 tip.IsOpen = true;
  tip.StaysOpen = true;

Through this tooltip is appearing on Windows loaded but not  at proper location. It should be appear below  "Radio button".  Please suggest me how will I fix this issue

Thanks