Best way for retrieving single record results in LINQ to SQL

Question

If I query a table with a condition on the key field as in:

        var user = from u in dc.Users
                   where u.UserName == usn
                   s         


        

Answer 1

Also it should be noted that First/FirstOrDefault/Single/SingleOrDefault are the point of execution for a LINQ to Sql command. Since the LINQ statement has not been executed before that, it is able to affect the SQL generated (e.g., It can add a TOP 1 to the sql command)

Answer 2

I would use the SingleOrDefault method.

var user = (from u in dc.Users
                   where u.UserName == usn
                   select u).SingleOrDefault();

Answer 3

Try something like this:

var user = (from u in dc.Users
                   where u.UserName == usn
                   select u).FirstOrDefault();

The FirstOrDefault method returns the first element of a sequence that satisfies a specified condition or a default value if no such element is found.

Answer 4

Why not something like

var user = dc.Users.SingleOrDefault(u=> u.UserName==usn);

Answer 5

Another option is to use Contains(username) as opposed to "=="

var user = (from u in dc.UserInfo 
                      where u.Users.Contains(username) 
                      select u).SingleOrDefault();

Answer 6

I would use First() or FirstOrDefault().

The difference: on First() there will be an exception thrown if no row can be found.