The view itself showed the correct results, but when called from code using the Entity Framework, it once again showed the wrong results.
After some testing I found out that the rows that were duplicated, were rows that shared certain values with the rows that were replaced by it. After checking this in my Entity Model, I soon found at that the Entity Model has a strange way of handling rows with equal primary key values.
I'll try and explain my findings:
If multiple rows share the same value in the primary column(s), only the first of these seems to be retrieved from the database and copied into these other rows. For instance, if a set has 2 columns, with the first being marked as the primary column, and the correct result should be:
A, 1
A, 2
B, 4
B, 6
B, 7
C, 5
The actual result in code with Entity Framework would become:
A, 1
A, 1
B, 4
B, 4
B, 4
C, 5
When including a view in your Entity Model, the model seems to simply use the first not-nullable columns as primary key (as all columns used in the primary key should be non-nullable).
To fix the problem, make sure that the primary key columns are chosen correctly. If you cannot create the correct primary key because of null-values or simply not having set of columns that differs for each row, try adding a column to your view that always contains a unique value for each row. After you add it, make sure it is set as the primary key in your Entity Model.
If I would set both rows to be the Primary Columns in the above example, I would get the desired result.
The following solution was given by Lee Boozer (thank you, Lee):
Add .AsNoTracking() to your Linq query. When you do this, EF returns the data as is, completely ignoring key definitions.
For instance:
context.vwItems.AsNoTracking().Where( ....
21 comments :
Thanks mate! I met the same issue and when I add PK to the view, it works now :)
Super Duper Blog Post...
I am struggling with same issue. But this article helps me a lot.
What i did is add a OW_NUMBER() OVER (ORDER BY R.ID ASC) AS ID for a view.
Then in the EF Model i set this as an Entity Key and thats it....
(I dont know how to set as a Primary key...)
Hi Kamal,
That's one way of adding a column with a unique value for each row. I prefer adding a PK column of one of the tables in the view, since nothing has to be generated. But if that's not possible, your solution is a reliable option.
I think entity calls the primary key the "entity key", but it's basically the same thing.
Regards,
Michael
Hi Kavitha,
It depends, what does make a unique identifier for a row in this view? Depending on how all your tables are related, I think you need a combination of an ID for the sale and and ID for each line in the sale. So I think combining SalesHeaderID and ItemID would be a good unique identifier, but it all depends on your data model, really.
Just try to set these as a combined Entity Key and see if it solves your problem.
Regards,
Michael
You're my hero of the day.
Genius, I'm grateful!
Why not try the "AsNoTracking()" method on the ObjectSet?
If you don't actually need unique records (for update purposes), by far the simplest solution is to add .AsNoTracking() to your Linq query. When you do this, EF returns the data as is, completely ignoring key definitions.
What you really want is:
ISNULL(ROW_NUMBER() OVER (ORDER BY ColumnName), - 1) AS PrimaryKeyId
to get the EF Model to treat it as a primary key. I'm not sure, but it's best to put this column first, so that EF can "guess" that it's the primary key.
Thanks buddy.
Excellent blog. It helped me a lot.
Thank you for this! Adding the AsNoTracking() method worked great. Wish EF was better at handling views.
Thanks that really helped!
Thank You, man! You saved my project and time! Thank you one more time!!!
Interesting stuff. Really grateful!
Thank you So much. AsNoTracking() solved my problem.
With your awsome information I was able to solve my problem with these painful duplicate rows. Great work!
Awesome information when entity frame work with key not having unique values
Tnx man, just save me a lot of time!!!
This was driving me nuts! Thank you!
Thank you!....your solution was VERY useful to me!!
Post a Comment