C
C#•4w ago
lime_soft

Entity Framework Core updating tables in navigation fields

so in efcore lets say i have an entity Foo and Baz: 
public class Foo 
{
  public int Id {get;set;}
  public ICollection<Baz> Bazs {get;set}
}

public class Baz 
{
  public int Id {get;set;}
  public string SomeOtherProp {get;set}
  public int FooId {get;set}
}
public class Foo 
{
  public int Id {get;set;}
  public ICollection<Baz> Bazs {get;set}
}

public class Baz 
{
  public int Id {get;set;}
  public string SomeOtherProp {get;set}
  public int FooId {get;set}
}
my question is if i try to update Foo how can i efcore to only update the FooId property in Baz if i pass Foo { Baz { Id: 1, FooId: 2 } }, i don't want Baz.SomeOtherProp to be null i just want it to stay the same
3 Replies
Yawnder
Yawnder•4w ago
You either do a roundtrip to get Baz first, or you use ExecuteUpdate.
Keswiik
Keswiik•4w ago
Alternatively, if you have Baz as a set on your dbcontext, you can instantiate a new instance of Baz and attach it, make your modification, then use SaveChanges() like normal. 
var newBaz = new Baz() {
  Id = someId
}
dbContext.Bazzes.Attach(newBaz);
// because you modify FooId after attaching, the change tracker detects FooId as the only modified field
newBaz.FooId = modifiedId;
dbContext.Save();
var newBaz = new Baz() {
  Id = someId
}
dbContext.Bazzes.Attach(newBaz);
// because you modify FooId after attaching, the change tracker detects FooId as the only modified field
newBaz.FooId = modifiedId;
dbContext.Save();
Doing it like this can be useful if you have multiple entities to modify with unique values
Unknown User
Unknown User•4w ago
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