You are implementing an application that uses Entity Framework-generated entities to update a data source. You add a method that retrieves a Product entity and changes its Status property. You need to ensure that the Entity Framework will throw an exception if a value in the data source changes between the time that your method retrieves the Product and the time the Product saves changes to it.

What should you do?

By default, the Entity Framework implements an optimistic concurrency model. This means that between the time when the data is queried and the time the data is updated, locks are not held on data in the data source. The Entity Framework saves object changes to the database without checking for concurrency. To ensure that values are checked for concurrency, you can define a property in the Entity Data Model's conceptual layer with an attribute of ConcurrencyMode="Fixed".

The ObjectContext's Refresh method updates an object in the object context with data from the data source. Setting the RefreshMode to StoreWins ensures that data source values overwrite client-side changes. This method does not throw an exception if the client values are different from data source values.