c# - "The data reader has more than one field" error in Entity Framework

Question

I'm executing this simple query with Entity Framework

db.Database.SqlQuery<string>("SELECT * FROM hospital");

But I got this error:

The data reader has more than one field. Multiple fields are not valid for EDM primitive or enumeration types.

What could be the problem?

Answer 1

It would be useful to see what the hospital table looks like but assuming something simple like hospital consists of HospitalId and HospitalName then you have a couple of choices.

//would work if all you're trying to do is get the Name:
db.Database.SqlQuery<IEnumerable<string>>("SELECT hospitalName FROM hospital"); 

//where you define MyEntity as the same structure as the table would work
db.Database.SqlQuery<MyEntity>("SELECT * FROM hospital"); 

// would theoretically work although I haven't tried it.  Where the Tuple 
// items would have to match the database types in order.  I.e. if field 1 
// is an int and field 2 is a string then Tuple<int,string>
db.Database.SqlQuery<IEnumerable<Tuple<int, string>>>("SELECT * FROM hospital");

Basically the error is the code doesn't know how to stuff the structure of hospital into a string