实体框架6投影生成等效于“ Select *”的SQL，并且不生成WHERE子句

Question

I'm maintaining an ASP.NET WebAPI2 application with Entity framework 6 and MSSQL server database. The IoC container is Castle Windsor. I have a method on my repository that I use to get some details for a user from DB. Since I don't need every column, I thought I'd use projection. The problem is that the generated SQL selects ALL the columns in my table. Here's the DbContext

public partial class SecurityContext : DbContext
{
    public SecurityContext()
        : base("name=SecurityContext")
    {
    }

    public virtual DbSet<User> secUsers { get; set; }
}

Here's where the context is declared/initialized in the repository

public class BaseRepository<T> : IRepository<T> where T : class
{
    protected DbContext context;

    public BaseRepository()
    {
        context = new SecurityContext();
    }

    public BaseRepository(DbContext context)
    {
        this.context = context;
    } 
    //elided
}

and here's the method in the repository

public User FindUserForLoginVerification(string name)
{         
    var loginInfo = context.Set<User>()
        .Where(c => c.LoginName == name)
        .Select(c => new 
        { 
            LoginName = c.LoginName, 
            Password = c.HashedPassword, 
            Salt = c.PasswordHashSalt 
        })
        .SingleOrDefault();

    return new User() { 
        LoginName = loginInfo.LoginName, 
        HashedPassword = loginInfo.Password, 
        PasswordHashSalt = loginInfo.Salt                
    };
}

Here's the output SQL.

SELECT 
[Extent1].[UserId] AS [UserId], 
[Extent1].[CreatedByUserId] AS [CreatedByUserId], 
[Extent1].[Comment] AS [Comment], 
[Extent1].[CreatedDate] AS [CreatedDate], 
[Extent1].[DefaultCulture] AS [DefaultCulture], 
[Extent1].[EmailAddress] AS [EmailAddress], 
[Extent1].[FirstName] AS [FirstName], 
[Extent1].[IsDeleted] AS [IsDeleted], 
[Extent1].[IsExcludedFromPasswordPolicy] AS [IsExcludedFromPasswordPolicy], 
[Extent1].[IsChangePassword] AS [IsChangePassword], 
[Extent1].[IsLocked] AS [IsLocked], 
[Extent1].[LastName] AS [LastName], 
[Extent1].[LastPasswordChangeDate] AS [LastPasswordChangeDate], 
[Extent1].[LoginName] AS [LoginName], 
[Extent1].[NumberOfFailedLoginAttempts] AS [NumberOfFailedLoginAttempts], 
[Extent1].[PasswordHash] AS [PasswordHash], 
[Extent1].[PasswordHashSalt] AS [PasswordHashSalt]
[Extent1].[UpdatedDate] AS [UpdatedDate]
FROM [dbo].[User] AS [Extent1]

I guess I'm doing something wrong, but I can't figure out what. Any ideas will be appreciated.

EDIT: I just noticed something strange - in the generated SQL there's no WHERE clause, which means that all the rows are selected from the database, brought to the client, and filtered there. EDIT 2: the same SQL is produced by using the LINQ query syntax. EDIT 3: After writing a unit test where I instantiate the repository and service manually (instead of leaving it to CastleWindsor), the SQL produced when running the test has the WHERE clause.

Answer 1

If your context is something that returns an IEnumerable<T> (and not IQueryable<T> ) from the Set<T> method, then that's your problem, because the expression:

context.Set<User>
.Where(...)
.Select(...)
.SingleOrDefault()

...will read the whole table into memory, and then apply the Where clause and the projection ( Select ). So, you would expect SELECT * FROM table behaviour.

The DbContext class implementation of Set<T> returns a DbSet<T> which does implement IQueryable<T> , so that would be OK. But since it looks like you have a custom repository implementation, I'm suspicious about what else might be going on behind the scenes...