如何在 EF4 中调用存储过程

Question

I'm trying to call a stored procedure in Entity Framework 4 application and so far getting strange results. Stored procedure takes IN and OUT parameters, and returns resultset. I mapped stored procedure and created a complex type that represents a row in returned resultset. I call it

using (MyObjectContext ctx = new MyObjectContext())
{
     ObjectParameter out1 = new ObjectParameter("out1", typeof(String));
     ObjectParameter out2 = new ObjectParameter("out2", typeof(String));     
     var res = ctx.my_proc(1,2, out1,out2);
}

The problem is that unless I call res.ToList() (or enumerate through res , or call any methods that accesses underlying collection), values of out1 and out2 are null .
How do I fix it?
Thanks

Answer 1

You cannot fix it. It is a gotcha. Result set must be materialized or thrown away before output parameters are accessible because these output parameters are transferred in the last result set so internal data reader must first read the returning result set with main data and then access the next result set to read output parameters. Btw. it is the same if you use ADO.NET directly - that is not a feature of Entity framework itself but the way how SQL server returns output parameters and the way how DataReader consumes result sets in sequential order.

Answer 2

when u call procedure or query that returns a table of rows EF does real execution when user calls ToList or enumerate the return value