The value of 'author_book.bookid' is unknown when attempting to save changes.

Question

1.00/5 (1 vote)

See more:

hi everybody
whats the cause and solution of the following error?

InvalidOperationException: The value of 'Author_Book.BookID' is unknown when attempting to save changes. This is because the property is also part of a foreign key for which the principal entity in the relationship is not known.

ASP.Net Core 5
EF Core 5.0.4

https://s17.picofile.com/file/8429178926/2021_03_30_162918.png[^]

Source : Dropbox - BookShop.rar - Simplify your life[^]

What I have tried:

in ASP.Net Core 2, Entity Framework Core 2 no problem...

Posted 30-Mar-21 2:20am

ahmadamiri

Updated 29-Nov-22 20:18pm

v2

Add a Solution

Comments

[no name] 30-Mar-21 11:46am

Find out what "BookID" is pointing to. Sounds like that "book" / id doesn't exist.

ahmadamiri 30-Mar-21 12:26pm

please see source "https://www.dropbox.com/s/mr7d16kq4f6g8nr/BookShop.rar?dl=0"
then run "Admin/Books/create"

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Zohidbek Mengliboyev · Answer 1 · 2022-11-29T20:18:00

Solution 1

Hi!

You forgot to write

C#

await _context.Books.SaveChangesAsync();

after this:

C#

await _context.Books.AddAsync(book);

Posted 29-Nov-22 20:18pm

Zohidbek Mengliboyev

v2

Comments

Richard Deeming 30-Nov-22 4:37am

The error message in the question clearly states that the error occurred when attempting to save changes. That would not happen if the OP had forgotten to call SaveChanges or SaveChangesAsync.

Zohidbek Mengliboyev 30-Nov-22 6:22am

Maybe, but I had a similar situation. That's why I gave the solution that worked for me.

Richard Deeming 30-Nov-22 6:59am

So you resurrected a question from last year to post an answer to a completely different question?

That sort of behaviour will get you banned from the site. If you're going to answer an old question, you need to make sure you're answering the question that was asked.

Zohidbek Mengliboyev 30-Nov-22 7:40am

You misunderstood my previous reply. My situation was the same as that person asked. When I couldn't find the answer, I googled it. Then I found recently this guy's project on CodeProject. Interestingly, his project's errors and exceptions were very similar to mine. Then I wrote an answer to this person's question only after I found the answer for my project. And this is not kind of behaviour that I will banned.

Richard Deeming 30-Nov-22 8:01am

The errors may be similar, but the fact that the error explicitly states "when attempting to save changes" suggests that "you forget to call SaveChangesAsync" is not the cause of the OP's error.

And to be honest, I fail to see how you could get an error "when attempting to save changes" and actually believe that the solution was that you had forgotten to save the changes.

Granted, the question you're answering is extremely poor; expecting someone else to download your entire project to diagnose the problem is a great way to get your question ignored or deleted.

Zohidbek Mengliboyev 30-Nov-22 9:10am

Thanks, got it.