Committing changes to the database using Entity Framework

Question

I have a situation where I pull data from a table by date. If no data is supplied for a given date I create a record using default values and display it all to the user. When the user is done manipulating the data I need to commit the changes.

So my question is how do I handle in Entity Framework submitting a table where there could be both updates and adds that need to be done. This is in C# using MVC3 and Entity Framework.

So here's what the data might look like to start,

Table A

NAME  AGE PHONE_NUM 
Jim   25  555-555-5555 
Jill  48  555-551-5555

After the users done with the data it could look like this,

Table A

NAME  AGE PHONE_NUM
Jim   25  555-555-5555
Jill  28  555-551-5555
Rob   42  555-534-6677

How do I commit these changes? My problem is there are both updates and inserts needed?

I've found some code like this but I don't know if it will work in this case.

For adding rows of data

entities.TABlEA.AddObject(TableOBJECT);
entities.SaveChanges();

or for updating data

entities.TABLEA.Attach(entities.TABLEA.Single(t => t.NAME == TableOBJECT.NAME));
entities.TABLEA.ApplyCurrentValues(TableOBJECT);
entities.SaveChanges();

Will any of this work or do I need to keep track of whats there and what was added?

Ideas?

Slauma · Accepted Answer · 2011-10-18 17:46:17Z

4

More or less you already have the solution. You just need to check if your Single call which tries to load the object from the DB has an result or not (use SingleOrDefault instead). If the result is null you need to insert, otherwise update:

foreach (var TableOBJECT in collectionOfYourTableOBJECTsTheUserWorkedWith)
{
    var objectInDB = entities.TABLEA
        .SingleOrDefault(t => t.NAME == TableOBJECT.NAME);
    if (objectInDB != null) // UPDATE
        entities.TABLEA.ApplyCurrentValues(TableOBJECT);
    else // INSERT
        entities.TABLEA.AddObject(TableOBJECT);
}
entities.SaveChanges();

(I'm assuming that NAME is the primary key property of your TableOBJECT entity.)

answered Oct 18, 2011 at 17:46

Slauma

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9 Comments

Dan Over a year ago

So whats the difference between Single and SingleOrDefault?

Wouter de Kort Over a year ago

Single checks if a query has only one result. If there is no result Single will throw an exception. SingleOrDefault checks for one result, if the query is empty it will return the Default value (most of the time NULL). So use Single when there should always be one result. Use SingleOrDefault when it's possible that there no result at all.

Dan Over a year ago

so it took me sometime to get to where I could use this and it's great except when it has to add more then one thing I get an exception from the DB complaining about not having unique keys. Ideas?

Dan Over a year ago

@Slauma: here's the exception it's on entities.SaveChanges(); "InvalidOperationException The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges."

Dan Over a year ago

I looked into it's a first chance exception and from what I can tell that means it could cause an exception later but didn't just now. So I'm catching it, ignoring it and everything keeps working fine. Does this sound safe or should I actually figure out how to stop it?

|

Mark Vincze · Accepted Answer · 2011-10-18 17:49:16Z

0

I think you have to keep track of what is new and what is modified. If you do that, that the two code examples you provided are going to work. A simple workaround which I used is to check if an entity's primary key property is set to anything. If it is set to a value, then that is an updated object, otherwise it's new.

Another solution would be to use Entity Framework's Self Tracking Entities, but I do not think that's the right direction to go in a web application (maybe it is in a distributed WCF app).

answered Oct 18, 2011 at 17:49

Mark Vincze

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