>Hi Rob and thanks a lot for your solution - one thing I had to change is the include - Instead of Include(inv => inv.client) I had to change it to Include("client") as it gave a compilation error - but other than that it works fine - thanks again.

The lambda version of the include function is an extension method rather than directly part of an ObjectQuery object. You would need to use the System.Data.Entity namespace to have that as an option. See http://msdn.microsoft.com/en-us/library/gg671236%28v=vs.103%29.aspx.