Changing identity fields

[Jurica]

Hi,

I have situation where entity with complex primary key (identities). Unfortunately, one of them is string/nvarchar (it is not in my power to change that). 

That table is presented on the form for the user so that he can define multiple N:N relationships. Besides identity fields there is one more string/nvarchar field (Description) that is part of the same table.


When I try to update keys/identity fields I get message: "Unsupported Operation: Change of identity is not supported."

When I change Description field and try to delete record/object and add the new entity  with same identities in same transaction I get:
"Instance of 'StanisteSvojtes' with identity '1120049971-A.1.1.1.1.-696' already exists in the cache of the object scope."

i cannot find solution.

Please advice.

[Ralph Waldenmaier]

Hi Jurica,
The scenario you are describing is expected. In general, changing the primary key is not supported by design.

To your second situation. When you are generating a new object with a primary key or loading it from the database, we are storing it in our first level cache of the context. Now when you are deleting the object and call SaveChanges, it will no longer be in the cache of the context and you can create the new one. If you omit the SaveChanges call, then you will receive the mentioned exception. See the following snippet of how it will work.

var id = Guid.NewGuid();
var usr = new User(){Id = id};
ctx.Add(usr);
ctx.SaveChanges();

ctx.Delete(usr);
ctx.SaveChanges();

var usr2 = new User(){Id = id};
ctx.Add(usr2);
ctx.SaveChanges();

I hope this information is helpful for you.
Do come back in case you need further assistance.


Regards,
Ralph Waldenmaier
Telerik