Calling a UDF with Entity SQL but without a FROM clause?

Am trying to call a UDF which just takes a parameter and returns a scalar. The examples I've seen all use a From clause: http://blogs.microsoft.co.il/blogs/gilf/archive/2009/10/20/calling-user-defined-functions-udfs-in-entity-framework.aspx

But I only want to call the UDF, I don't want to "join" it with any entities using a from clause:

  string fieldTag = "TagNameHere";
  var sql = "SELECT XyzModel.Store.FieldNameToFormIdMap(@fieldTag)";
  System.Data.Objects.ObjectQuery<int> query =
    new System.Data.Objects.ObjectQuery<int>(sql, xyzEntitiesContext);
  query.Parameters.Add(new System.Data.Objects.ObjectParameter("fieldTag", fieldTag));

I get the error: "The q开发者_开发问答uery syntax is not valid."

This is using .NET 3.5

I could use old style ADO.NET but I'd rather not have to manage another set of connection strings aside from those used for the entity framework.

Just remove SELECT from your query, like this:
var sql = "XyzModel.Store.FieldNameToFormIdMap(@fieldTag)";