Pass Entity Framework type to generic method

Question

In my project using Entity Framework, I have a bunch of functions that look almost exactly alike, so I want to created a generic method they call:

private IHttpActionResult GetData<TEntity>(DbSet<TEntity> data)

The problem I'm having is that the data parameter is saying TEntity has to be a reference type to work, but the type of the entity comes from auto-generated code that doesn't have any base class that I can constrain via a where clause on the method definition.

I'd basically want to call it by getting a context and passing the table in like so:

using (var context = new DataModel.MyEntities()) {
    GetData(context.Lab_SubSpace_Contact);
}

private IHttpActionResult GetData<TEntity>(DbSet<TEntity> data) where TEntity : class <=== Why can't you do that? — Igor
– Igor, Commented Mar 15, 2018 at 21:56
When it says the TEntity has to be a reference type it means that as an unconstrained generic type it can be either a reference or a value type. Igor has given you the constraint that will limit the generic type to a reference types class. — juharr
– juharr, Commented Mar 15, 2018 at 21:58
Cause I didn't realize I could just do that :) It won't let me accept your answer for 9 more minutes. Thanks for the quick solution. — Gargoyle
– Gargoyle, Commented Mar 15, 2018 at 21:59

Camilo Terevinto · Accepted Answer · 2018-03-15 22:02:38Z

3

To expand on @Igor's answer, you don't have to pass the DbSet<TEntity>, you can also get that dynamically through the type parameter:

private IHttpActionResult GetData<TEntity>() where TEntity : class
{
    using (var context = new YourContext())
    {
        var dbSet = context.Set<TEntity>();
    }
}

answered Mar 15, 2018 at 22:02

Camilo Terevinto

32.2k7 gold badges95 silver badges127 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Gargoyle Over a year ago

Very cool! This definitely makes the DB connection cleaner too.

Igor · Accepted Answer · 2018-03-15 21:58:01Z

2

You do not need a base class, you only have to specify a constraint that it has to be a class (not a struct). This can be done with where TEntity : class

Constraints on Type Parameters

where T : class : The type argument must be a reference type; this applies also to any class, interface, delegate, or array type.

Modified code

private IHttpActionResult GetData<TEntity>(DbSet<TEntity> data) where TEntity : class

answered Mar 15, 2018 at 21:58

Igor

62.5k10 gold badges111 silver badges181 bronze badges

Collectives™ on Stack Overflow

Pass Entity Framework type to generic method

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related