LINQ to SQL：插入子实体失败，因为SQL中不包含ID？

Question

I'm doing a very simple insert into a database by assigning the child of an LINQ-to-SQL entity, but it's failing on the foreign key.

The code is:

var imageStripFileAltText = new ImageStripFileAltText();
imageStripFileAltText.Alt = "alt text";
imageStripFile.ImageStripFileAltText = imageStripFileAltText;
db.SubmitChanges();

imageStripFile is a custom type ImageStripFile with a corresponding table in the database.
db is a DataContext.

When I inspect imageStripFile.ImageStripFileAltText in the debugger, I see that it has been assigned the correct foreign key Id, that is, the primary key of imageStripFile . However, I get the following Exception:

System.Data.SqlClient.SqlException: 'The INSERT statement conflicted with the FOREIGN KEY constraint "FK_ImageStripFileAltText_ImageStripFile". The conflict occurred in database "Cms", table "dbo.ImageStripFile", column 'Id'.

Since I made sure the ImageStripFile with the corresponding ID exists, this baffled me, until I inspected the generated SQL:

DECLARE @p0 NVarChar(4000) = 'alt text' 
INSERT INTO [dbo].[ImageStripFileAltText]([Alt])
VALUES (@p0)

The generated SQL does not include the ID in the parameters!

What am I doing wrong?

I've also tried directly assigning the foreign key ID:

var imageStripFileAltText =
    new ImageStripFileAltText() { ImageStripFileId = imageStripFile.Id };

but the result is the same.

Edit: If I remove the IsIdentity property from the child table's primary key (which I now believe is the correct situation), I get a different Exception:

System.Data.SqlClient.SqlException: 'Cannot insert the value NULL into column 'ImageStripFileId', table 'Cms.dbo.ImageStripFileAltText'; column does not allow nulls. INSERT fails.

Note that this corresponds with the generated SQL as well.

Answer 1

In my scenario, the PK field in my table was not auto incremented ie IsIdentity was set to false. Try checking this in your tables.

Answer 2

Wow. I was building my model on the Development Database and executing the code on the Production Database, on which the ImageStripFileAltText table had a slightly different scheme (probably something with IsIdentity?), since I was still tinkering with it when I wrote the code.

Long story short: the code is fine; don't be an idiot and work diligently.

Answer 3

IsIdentity需要设置为true并自动递增