EF Core Find breaks with Nullable Id

Question

Using EF Core 1.1 and Asp Core 1.1 on Mac

With a model like

public class Model {
  public int? Id { get; set; }
  public string OtherProp { get; set; }
}

And an action

public class ModelController
{
    public Model Get(int? id) 
    {
      DbContext.Set<Model>.Find(id)
    }
}

Accessing the url /model/10 fails with a message The key value at position 0 of the call to 'DbSet<Model>.Find' was of type 'int', which does not match the property type of 'Nullable<int>'

The error message is clear but my question is if there is a way to make this work, it seems like a very common use case and one that used to work in previous versions.

I tried casting id to int? but it didn't work. Any ideas?

Also, in case it's useful this is the line that's breaking in EF

Why do you have a private setter (how could the value be set)? — , Feb 03 '17 at 04:58
I'm pretty sure that works with EF setting the value, but anyway, I tried making it public and got the same error. — jorgehmv, Feb 03 '17 at 05:01
It was more related to how you would ever be able to bind the model when you submitted a form - it needs to be `public` — , Feb 03 '17 at 05:02
Gotcha, this is an oversimplified example just to focus on the error so I'll edit the setter so that it doesn't make more noise — jorgehmv, Feb 03 '17 at 05:04
is that a "nullable" primary key? Can primary key be nullable? — Developer, Feb 03 '17 at 05:13
For new instances it can be null, previous versions of EF allowed this. It's a small difference to check `Id.HasValue` vs `Id != 0`. I realize making it `int` would work but it'd be nice to keep it as `int?` — jorgehmv, Feb 03 '17 at 05:16
@jorgehmv - my doubt was whether database supports null for primary key? — Developer, Feb 03 '17 at 08:09

score 2 · Answer 1 · edited May 23 '17 at 12:09

Looking at the code you've already linked: this cannot work, since the CLR gives you always the underlying type for a null-able instance. (Don't know why, had similar issues before...)

In code: typeof(int?) != ((int?)1).GetType().

Thus, comparing the type of the property (int?) and the type of the argument will always fail. You have to ask the EF Core team to add support for null-able types for that.

Related: Nullable type is not a nullable type?

EF Core Find breaks with Nullable Id

1 Answers1