UrlEditor not working

[maxcocco]

Hello,
I'm building a custom WebControl and I'm trying to use the UrlEditor
for the following property.
The property is displayed correctly in the property browser, but when I
click the ellipses button, nothing happens.
What's wrong with this code?

Thanx,
Max

private string _xmlMappingUrl;
[Category("EntityBinding")]
[Editor(typeof(System.Web.UI.Design.UrlEditor),typeof(System.Drawing.Design.UITypeEditor))]
public string XmlMappingUrl
{
get { return _xmlMappingUrl; }
set { _xmlMappingUrl = value; }
}