The RoundedCorners extender applies rounded corners to existing elements. To accomplish this it inserts elements before and after the element that is selected, so the overall height of the element will change slightly. You can choose the corners of the target panel that should be rounded by setting the Corners property on the extender to None, TopLeft, TopRight, BottomRight, BottomLeft, Top, Right, Bottom, Left, or All.

The control above is initialized with this code. The italic properties are optional.

<ajaxToolkit:RoundedCornersExtender ID="rce" runat="server"

    TargetControlID="Panel1"

    Radius="6"

    Corners="All" />

    * TargetControlID - The ID of the button or link for this extender to operate on

    * Radius - The radius of the corners (and height of the added area). Default is 5.

    * Corners - The corners of the target panel that will be rounded (can be None, TopLeft, TopRight, BottomRight, BottomLeft, Top, Right, Bottom, Left, or All)