LINQ to Entities does not recognize the method 'Int32 Parse(System.String)' why?

I have code

 foreach (XElement t in selxml.Elements("Type"))
                printxml.Add(new XElement("Type",
                    new XAttribute("TypeID", t.Attribute("ID").Value),
                    new XAttribute("TypeName", (from pt in fdb.PrintTypes where pt.PrintTypeID == Int32.Parse(t.Attribute("ID").Value) select pt.Name).SingleOrDefault()),
                    new XAttribute("Value", t.Attribute("Value").Value),
                    new XAttribute("ValueName", (from pti in fdb.PrintTypeItems
                                                 where pti.Value == Int32.Parse(t.Attribute("Value").Value) &&
                                                       pti.PrintTypeID == Int32.Parse(t.Attribute("ID").Value)
                                                 select pti.Name).SingleOrDefault())));

and VS say

LINQ to Entities does not recognize the method 'Int32 Parse(System.String)' method, and this method cannot be translated into a store expression.

why LINQ to Entities? this is Linq to XML. How can I solve this problem?

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