xml to linq query where letter starts with a in windows phone

i am trying to fetch data where all words starting with A and displaying it listbox using xml to LINQ, but the Startwith property i am not able acheve here is the code i am trying to fetch

XDocument loadedCustomData = XDocument.Load("accounts.xml");
            var filteredData =
               from c in loadedCustomData.Descendants("record")

               where  (string)c.Element("main") == "Above the Line"
                // i want here something like
                //where (string)c.element("main").startwith ==a
                //so how to ACHIEVE THIS????
               select new words()
               {

                   PON = "Post Office: " + (string)c.Element("main"),
                   PIN = "Pincode (Postal Code): " + (string)c.Element("def"),

               };
            listBox1.ItemsSource = filteredData;

SO HOW TO ACHIEVE THE QUERY TO START WITH LETTER A