Why is my DbContext DbSet null?

Question

I created a new Entity Frameworks Code First app and the DbSet (People) is returning null.

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Repository : DbContext
{
    public DbSet<Person> People;
}

web.config: connection string

<connectionStrings>
  <add name="Repository"
       connectionString="Data Source=|DataDirectory|Repository.sdf"
       providerName="System.Data.SqlServerCe.4.0"/>
</connectionStrings>

Now when I call

Repository _repo = new Repository()
_repo.People;

_repo.People will be null

What I am missing?

Microsoft.Data.Entity.Ctp.dll is referenced
I have tried with and without a database initializer.

score 93 · Accepted Answer · edited Jun 27 '12 at 12:10

93

That's because you define a field of DbSet<Person> on Repository class instead of a property. Once you add a property or change it to be a automatic property,People will start to give you values instead of null. So all you need to do is to change your Repository class to:

public class Repository : DbContext
{
    public DbSet<Person> People { get; set; }
}

edited Jun 27 '12 at 12:10

Richard Ev

52,939
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answered Nov 24 '10 at 22:12

Morteza Manavi

33,026
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7

It can also come up null if you try to use `{ get; private set; }`. EF doesn't like that. – Ryan Lundy May 10 '14 at 23:19
3

Nor should the setter be protected. It should be public: `{ get; set; }` – arni Aug 31 '16 at 13:30
If the data source is a SQL view, can I skip the setter? – ARLibertarian Jun 26 '19 at 15:21
Also, the access modifier *must* be public – Najeeb Mar 24 '20 at 11:33

score 51 · Answer 2 · answered Aug 04 '11 at 16:16

51

I just had the same issue. The problem was that I did set these properties as 'internal' while they must have been 'public'. Just in case someone is still searching :)

answered Aug 04 '11 at 16:16

Martynas

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anyone know why you can set them to internal at all? – Guy Lowe May 30 '14 at 00:10
1

@GuyLowe Because a db context is just another class. C# analysers haven't always been clever enough to flag these things as warnings. Now I'm wondering whether the same issue exists in .NET Core/EF Core. – Alternatex Jan 18 '22 at 14:34

score 5 · Answer 3 · answered Dec 15 '15 at 15:07

5

I just had the same issue. The problem was that I did set these properties as 'internal' while they must have been 'public'. Just in case someone is still searching :)

I guess, these properties can be internal/public too, if you use them like this:

public class Repository : DbContext
{
    internal DbSet<Person> People { get; set; }

    public Repository()
    {
        //your code here...
        People = Set<Person>();
    }
}

answered Dec 15 '15 at 15:07

denisv

319
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That's a very clever way to have the best of both worlds. Thanks – Romain Vergnory Apr 12 '19 at 09:09

Why is my DbContext DbSet null?

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