Entity Framework add many entities, nested properties are already existing

Question

I need to add many entities at once. This is not complex:

EntityType entities = GetEntities();
dbContext.MyTable.AddRange(entities);

However each entity references another sub property (that is already existing, and for which I know the id). Is there an efficient way to avoid querying in advance all the subproperties?

for (int i = 0; i < entities.Length; i++)
{
    // adding already existing property 
    entities[i].MyProperty = new MyProperty { Id = ExternalIds[i] };
}

dbContext.MyTable.AddRange(entities); // Don't want to create new entities

rekiem87 · Accepted Answer · 2018-09-25 16:04:02Z

3

You can create the empty entity object with just the id, you could also add the property key to your entity

public class Course
{
  public int CourseID { get; set; }
  public string Title { get; set; }
  public int Credits { get; set; }
  public int DepartmentID { get; set; }
  public virtual Department Department { get; set; }
}

Here, you could just put the DepartmentID value and save, or

Course.Department = new Department{ id = 123 }

The docs says

If the reference is in the added state (in this example, the course object), the reference navigation property will not be synchronized with the key values of a new object until SaveChanges is called.

answered Sep 25, 2018 at 16:04

rekiem87

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Moho · Accepted Answer · 2018-09-25 16:12:45Z

0

Two solutions, first you can attach the related entity object manually so that it is tracked in the unchanged state prior to adding the target entity object:

var myProps = ExternalIds
    .Select( id => new MyProperty { Id = id } )
    .ToArray();

dbContext.AttachRange( myProps ); // tracks as Unchanged

...
entities[ i ].MyProperty = myProps[i];

Or expose the FK property for the nav property and simply set the ID (which is my preferred solution if you're working with the FK values)

public class EntityType
{
    ...
    public int MyPropertyId { get; set; }
    [ForeignKey( "MyPropertyId" )]
    public MyProperty MyProperty { get; set; }
}

...
Entities[i].MyPropertyId = ExternalIds[i]

answered Sep 25, 2018 at 16:12

Moho

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