I think you have a mistake in where condition, see below:
feed.Attribute("id") returns XAttribute class so you can't use equals to compare to a string, but after Value property you can.
var feeds = from feed in xDoc.Descendants("name")
where feed.Attribute("id").Value.Equals("Test1")
select new
{
fxfv = feed.Attribute("SharepointGroup").Value
};