Why does Select return a boolean?

Question

Why does Select return a boolean?

asp.net-mvc-5 c# entity-framework-6 linq

Question

I'm working with Entity Framework 6 in MVC 5.

I have the following method:

[HttpPost]
public ActionResult UpdateDetails(ApplicationUser applicationUser)
{
    var context = new ApplicationDbContext();
    var user = context.Users.Select(x => x.UserName == applicationUser.UserName).FirstOrDefault();

//etc etc
}

Users is an IDbSet<ApplicationUser>.

Why am I getting a bool back from the Select method?

My expectation would be to get an ApplicationUser object back. Why isn't this the case?

Thanks

prisoner24601

Popular Answer

Select literally selects something inside the arguments. So, if you have an expression that returns a bool, Select will return bool.

Leonel Sanches da Silva

View more on Stack Overflow

Henk Mollema · Accepted Answer · 2/19/2014 9:27:07 PM

Select() projects an element of a sequence. Since x.UserName == applicationUser.UserName returns a bool, the result of the method will be a boolean.

What you want requires the Where method. This filters the sequence based on the specified predicate:

var user = context.Users.Where(x => x.UserName == applicationUser.UserName).FirstOrDefault();

Which can be shortened to:

var user = context.Users.FirstOrDefault(x => x.UserName == applicationUser.UserName);

This is possible, since this overload of FirstOrDefault() takes a filter predicate as second parameter.

Why does Select return a boolean?

Question

Fastest Entity Framework Extensions

Accepted Answer

Popular Answer

Performance

Expression Evaluator

Related