Eager loading for one to many to one in EF Core

Question

Eager loading for one to many to one in EF Core

asp.net-core c# entity-framework entity-framework-core

Question

I have a database schema just like below:

Here is the code that I need to do eager loading for my data:

var item = db.Course
    .Include(p => p.CourseInstructor)
    .FirstOrDefault(p => p.CourseId == courseId);

if (item == null)
{
    return NotFound();
}

return (from p in item.CourseInstructor
        select p.Instructor).ToList();

All I can get are the null on the p.Instructor navigation property.

I was tried to use ThenInclude, but I don't know how to code it right.

How can I made this code works as expected to get the full Person data using Eager loading technique?

Will Huang

View more on Stack Overflow

Ivan Stoev · Accepted Answer · 10/10/2018 8:06:29 PM

This is a known Intellisense issue with the ThenInclude overload for collection type navigation properties, tracked by the Completion missing members of lambda parameter in fault tolerance case #8237 Roslyn GitHub issue.

Until it gets fixed, simply type the name of the property and it will compile successfully and work as expected.

.ThenInclude(mu => mu.ParseSubTrees)

Update: Now it's even specifically mentioned in the Including multiple levels section of the EF Core documentation:

Note

Current versions of Visual Studio offer incorrect code completion options and can cause correct expressions to be flagged with syntax errors when using the ThenInclude method after a collection navigation property. This is a symptom of an IntelliSense bug tracked at https://github.com/dotnet/roslyn/issues/8237. It is safe to ignore these spurious syntax errors as long as the code is correct and can be compiled successfully.

Eager loading for one to many to one in EF Core

Question

Fastest Entity Framework Extensions

Accepted Answer

Performance

Expression Evaluator

Related