/// <summary>
/// Get attribute value of element at the given x,y location by given key.<br/>
/// If more than one element exist with the attribute at the location the inner most is returned.
/// </summary>
/// <param name="location">the location to find the attribute at</param>
/// <param name="attribute">the attribute key to get value by</param>
/// <returns>found attribute value or null if not found</returns>
public string GetAttributeAt(RPoint location, string attribute)
{
ArgChecker.AssertArgNotNullOrEmpty(attribute, "attribute");
var cssBox = DomUtils.GetCssBox(this._root, this.OffsetByScroll(location));
return(cssBox != null?DomUtils.GetAttribute(cssBox, attribute) : null);
}