Update is setting value to null in Entity Framework Core

Question

I'm using EF Core 2.2.4 and I'm running into very strange behavior.

Given the following code snippet:

var warrantyRegistrationId = warrantyRegistration.Id;  // warrantyRegistration.Id = 20

var order = ctx.Orders  // Id = 13
    .Where(x => x.CompanyId == 1 && x.CustomerId == warrantyRegistrationModel.CustomerId && x.IsDeleted == false && x.WarrantyRegistrationId == null)
    .FirstOrDefault();

var originalOrder = ctx.Orders    // Id = 12
    .Where(x => x.Id == order.OriginalOrderId)
    .FirstOrDefault();

order.WarrantyRegistrationId = warrantyRegistrationId; // order.WarrantyRegistrationId = 20
originalOrder.WarrantyRegistrationId = warrantyRegistrationId;  // originalOrder.WarrantyRegistrationId = 20
ctx.SaveChanges();  

// order.WarrantyRegistrationId = null, originalOrder.WarrantyRegistrationId = 20

Somehow the first assignment order.WarrantyRegistrationId = warrantyRegistrationId; is being set to null in the database.

When I run Sql Server profiler, I see the following:

exec sp_executesql N'SET NOCOUNT ON;
UPDATE [Orders] SET [WarrantyRegistrationId] = @p0
WHERE [Id] = @p1;
SELECT @@ROWCOUNT;
',N'@p1 int,@p0 int',@p1=12,@p0=20

and

exec sp_executesql N'SET NOCOUNT ON;
UPDATE [Orders] SET [WarrantyRegistrationId] = @p0
WHERE [Id] = @p1;
SELECT @@ROWCOUNT;
',N'@p1 int,@p0 int',@p1=13,@p0=NULL

I'm stuck and can't figure out why this is happening.

Any ideas?

Scottie · Accepted Answer · 2019-12-27 19:52:20Z

1

In case anybody else runs into this, here's the answer.

I had set this as .HasOne().WithOne(), which created a unique index on WarrantyRegistrationId. Since I was assigning a new Id, it was removing it from the previous WarrantyRegistrationId to keep it unique.

I changed this to .HasOne().WithMany() and it's working now.

answered Dec 27, 2019 at 19:52

Scottie

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