Entity Framework and SQL Server View

Question

We had the same problem and this is the solution:

To force entity framework to use a column as a primary key, use ISNULL.

To force entity framework not to use a column as a primary key, use NULLIF.

An easy way to apply this is to wrap the select statement of your view in another select.

Example:

SELECT
  ISNULL(MyPrimaryID,-999) MyPrimaryID,
  NULLIF(AnotherProperty,'') AnotherProperty
  FROM ( ... ) AS temp

I was able to resolve this using the designer.

1. Open the Model Browser.
2. Find the view in the diagram.
3. Right click on the primary key, and make sure "Entity Key" is checked.
4. Multi-select all the non-primary keys. Use Ctrl or Shift keys.
5. In the Properties window (press F4 if needed to see it), change the "Entity Key" drop-down to False.
6. Save changes.
7. Close Visual Studio and re-open it. I am using Visual Studio 2013 with EF 6 and I had to do this to get the warnings to go away.

I did not have to change my view to use the ISNULL, NULLIF, or COALESCE workarounds. If you update your model from the database, the warnings will re-appear, but will go away if you close and re-open VS. The changes you made in the designer will be preserved and not affected by the refresh.

Agree with @Tillito, however in most cases it will foul SQL optimizer and it will not use right indexes.

It may be obvious for somebody, but I burned hours solving performance issues using Tillito solution. Lets say you have the table:

 Create table OrderDetail
    (  
       Id int primary key,
       CustomerId int references Customer(Id),
       Amount decimal default(0)
    );
 Create index ix_customer on OrderDetail(CustomerId);

and your view is something like this

 Create view CustomerView
    As
      Select 
          IsNull(CustomerId, -1) as CustomerId, -- forcing EF to use it as key
          Sum(Amount) as Amount
      From OrderDetail
      Group by CustomerId

Sql optimizer will not use index ix_customer and it will perform table scan on primary index, but if instead of:

Group by CustomerId

you use

Group by IsNull(CustomerId, -1)

it will make MS SQL (at least 2008) include right index into plan.

If

This method works well for me. I use ISNULL() for the primary key field, and COALESCE() if the field should not be the primary key, but should also have a non-nullable value. This example yields ID field with a non-nullable primary key. The other fields are not keys, and have (None) as their Nullable attribute.

SELECT      
ISNULL(P.ID, - 1) AS ID,  
COALESCE (P.PurchaseAgent, U.[User Nickname]) AS PurchaseAgent,  
COALESCE (P.PurchaseAuthority, 0) AS PurchaseAuthority,  
COALESCE (P.AgencyCode, '') AS AgencyCode,  
COALESCE (P.UserID, U.ID) AS UserID,  
COALESCE (P.AssignPOs, 'false') AS AssignPOs,  
COALESCE (P.AuthString, '') AS AuthString,  
COALESCE (P.AssignVendors, 'false') AS AssignVendors 
FROM Users AS U  
INNER JOIN Users AS AU ON U.Login = AU.UserName  
LEFT OUTER JOIN PurchaseAgents AS P ON U.ID = P.UserID

if you really don't have a primary key, you can spoof one by using ROW_NUMBER to generate a pseudo-key that is ignored by your code. For example:

SELECT
ROW_NUMBER() OVER(ORDER BY A,B) AS Id,
A, B
FROM SOMETABLE