.NET Core 2 - EF Core Error handling Save changes

Question

I'm used to Entity Framework 6 and my base repository Save() looks like this:

public void Save()
{
    try
    {
        Context.SaveChanges();
    }
    catch (DbEntityValidationException ex)
    {
        // Do stuff
    }
    catch (Exception exception)
    {
        // Do stuff
    }
    else
    {
        throw;
    }
}

DbEntityValidationException is an expected error from Entity Framework if the object save is invalid. Now that I'm on a new .NET Core 2 project. What is the expected entity validation error type in Entity Framework Core?

Solution

Looking through the GitHub issues, there is no DbEntityValidationException equivalent in Entity Framework Core. There's a blog post (linked from issue #9662 on GitHub), that gives a code example for performing the validation logic yourself, included here for completeness:

class MyContext : DbContext
{
    public override int SaveChanges()
    {
        var entities = from e in ChangeTracker.Entries()
                       where e.State == EntityState.Added
                           || e.State == EntityState.Modified
                       select e.Entity;
        foreach (var entity in entities)
        {
            var validationContext = new ValidationContext(entity);
            Validator.ValidateObject(entity, validationContext);
        }

        return base.SaveChanges();
    }
}

Validator.ValidateObject will throw a ValidationException if validation fails, which you can handle accordingly.

There's a bit more information in the linked issue in case you run into issues with the validation attributes.

---

Note: The Validator class is located in the System.ComponentModel.DataAnnotations namespace.

Comments

[DavidG]

Did you think of trying to see what exception is thrown?

[Dmitry]

"Exception" is always "unexpected". If you "expect" some "exceptional situation" (BTW, why you don't prevent it?) - it's your app-specific.

[Chris Bordeman]

Doesn't do referential integrity, just data annotation style validations.

[James White]

There is also a TryValidateObject which lets you collect the errors without throwing an excepton.

[dan]

If you need to include additional validations such as MinLength you may have to add the validateAllProperties bool parameter as: Validator.ValidateObject(entity, validationContext, validateAllProperties: true)