entity framework core - virtual property will not update to null - Stack Overflow

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I am working with 2 entities: Hospital Facility The hospital has a one-to one relationship with facility that is nullable. I added public virtual Facility Facility to the Hospital entity and did a migration:

public class Hospital
{
    public virtual Facility Facility { get; set; }
}

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

All looks good in the database. A nullable FacilityId foreign key has been added to the Hospital table. I can set that value to null directly through MMSM. However, when I try and do this through code, it will not update/set to null. Here's my last attempt:

if (facilityId != null)
{
    hospital.Facility = _dbContext.Facility.Find(facilityId);
} 
else
{
    hospital.Facility = null;
}

_dbContext.Hospital.Update(hospital);

So odd, has anyone ran into this issue?

I am working with 2 entities: Hospital Facility The hospital has a one-to one relationship with facility that is nullable. I added public virtual Facility Facility to the Hospital entity and did a migration:

public class Hospital
{
    public virtual Facility Facility { get; set; }
}

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

All looks good in the database. A nullable FacilityId foreign key has been added to the Hospital table. I can set that value to null directly through MMSM. However, when I try and do this through code, it will not update/set to null. Here's my last attempt:

if (facilityId != null)
{
    hospital.Facility = _dbContext.Facility.Find(facilityId);
} 
else
{
    hospital.Facility = null;
}

_dbContext.Hospital.Update(hospital);

So odd, has anyone ran into this issue?

• entity-framework-core

Share Improve this question Follow edited Jan 22 at 12:21 Svyatoslav Danyliv 27.3k44 gold badges2121 silver badges3939 bronze badges asked Jan 21 at 21:53 user1231748user1231748 13711 silver badge1010 bronze badges 3

• For some reason, it still creating a facility on the hospital and setting the id = 0 instead of allowing null – user1231748 Commented Jan 21 at 23:03
• What is the value of facilityId here: if (facilityId != null). Is it null? Or zero? – devlin carnate Commented Jan 21 at 23:17
• It is null and hits the breakpoint in the Else. Another thing is when I add a new hospital with no facility it works correctly/is null in the database. The issue is only when trying to remove a facility from a hospital that already has one. – user1231748 Commented Jan 22 at 14:02

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1 Answer 1

Sorted by: Reset to default 2

If the relationship is optional then make the navigation property and any FK null-able:

public class Hospital
{
    public virtual Facility? Facility { get; set; }
}

Your code example did not include a call to SaveChanges() so nothing would be persisted in that case.

The next important step when updating an existing Hospital, ensure any existing Facility is eager loaded. Avoid using Update and detached entities when working with related entity graphs. Fetch the entity and transfer values across. Simpler and safer.

var hospital = _dbContext.Hospitals
    .Include(h => h.Facility)
    .Single(h => h.HospitalId == hospitalId);

if (facilityId != null)
    hospital.Facility = _dbContext.Facility.Find(facilityId);
else
    hospital.Facility = null;

_dbContext.SaveChanges();

If you are updating an existing hospital that had a facility ID set and you want to clear it because an updated facility reference was removed then EF needs to know that there "was" a facility associated with the hospital and you intend to remove it by setting it to #null. If you fetch a hospital without eager loading the existing facility then the property is already #null so the change tracker doesn't pick up on anything to update. Calls to Update() could result in a #null being written but it is generally better to avoid Update() as it can lead to data overwrites you don't intend.

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