Entity Framework Core .Select() - SQL has all columns not the specified subset

Question

I am doing a simple query with a .Select() on a database view and was expecting to see a shorter list of columns in the generated SQL:

DbContext.LeadSearch.Select(ls => new
        {
            ls.Id,
            ls.BrokerName,
            ls.UpdateDate
        }).Take(2).ToList();

The generated SQL included all of the columns though:

SELECT TOP(@__p_0) [ls].[Id], [ls].[AssetNumber], [ls].[BrokerId],
[ls].[BrokerName], [ls].[FirstName], [ls].[IsApproved],
[ls].[LastName], [ls].[PurchaseAmount], [ls].[Yadda], [ls].[Yadda2], 
... [ls].[UpdateDate] FROM [dp].[vwLeadSearch] AS [ls]

From what I have read elsewhere I was expecting the SQL to have just the "Selected" columns.

LeadSearch is defined as a DbSet:

public DbSet<LeadSearch> LeadSearch { get; set; }

Mapped to the view:

modelBuilder.Entity<LeadSearch>().ToTable("vwLeadSearch").HasKey("Id");

This is with EF Core 2.1.1.

If LeadSearch is a DbSet and the entity class is mapped properly, yes. — Gert Arnold
– Gert Arnold, Commented Aug 14, 2018 at 9:53
Can you provide more context because what you are describing does not happen with DbSets. When you say database view, how it is mapped in EF Core - DbSet or DbQuery with ToView? — Ivan Stoev
– Ivan Stoev, Commented Aug 14, 2018 at 12:00
@IvanStoev Question has been edited. Notat that the .Select() works as expected on a table. I also tried switching the view to use modelBuilder.Query<LeadSearch>().ToView("vwLeadSearch") but the SQL statement still contained all columns. — Jersey Dude
– Jersey Dude, Commented Aug 14, 2018 at 19:54
Thanks. Unfortunately I can't reproduce using both approaches - I'm getting just the selected columns as expected. — Ivan Stoev
– Ivan Stoev, Commented Aug 14, 2018 at 20:04
@IvanStoev Thanks for proving that it works as expected. It helped me track down what I was doing wrong, — Jersey Dude
– Jersey Dude, Commented Aug 16, 2018 at 0:55

Jersey Dude · Accepted Answer · 2018-08-16 00:54:24Z

2

One of the "columns" I included in the Select() was actually a calculated property on the class:

public string Name => FirstName + " " + LastName;

EF was smart enough to know it had to get all of the columns in order for this expression to complete. Changing my Select to get FirstName and LastName instead of Name fixed the issue.

answered Aug 16, 2018 at 0:54

Jersey Dude

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