RoundedCorners控件是专门用来锐化边角的工具和DropShadow控件的锐化效果一样，但是没有阴影效果，优点是可以只锐化4个边角中的任意一个或多个。
属性列表：
TargetControlID:要锐化的控件ID
Radius:锐化幅度
Corners:要锐化的边角，ALL表示所有边角
实例解析一、简单实现
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
</div>
<cc1:RoundedCornersExtender ID="RoundedCornersExtender1" runat="server" TargetControlID="Button1" Radius="20" Corners="All">
</cc1:RoundedCornersExtender>
<asp:Button ID="Button1" runat="server" Text="锐化效果" />
</form>
实例解析二、简单实现二
<head runat="server">
<title>RoundedCorners Demo</title>
<link href="StyleSheet.css" rel="stylesheet" type="text/css" />
<style type="text/css">
.loginPanel
{
background-color: #ddd;
width: 210px;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="sm" runat="server" />
<asp:Panel ID="loginPanel" CssClass="loginPanel" runat="server">
<asp:Login ID="myLogin" CssClass="loginPanel" runat="server">
</asp:Login>
</asp:Panel>
<ajaxToolkit:RoundedCornersExtender ID="rce" TargetControlID="loginPanel" Radius="10" Color="#dddddd"
runat="server" />
</form>
</body>