Handling concurrent updates in ASP.NET Web API 2 can be tricky, as multiple requests can attempt to modify the same data simultaneously, potentially leading to data inconsistencies. To address this issue, you can implement optimistic concurrency control (OCC) mechanisms, which ensure that data remains consistent even in the face of concurrent updates.
Optimistic Concurrency Control (OCC)
OCC relies on the assumption that conflicts are rare, and it attempts to resolve them without blocking other requests. It achieves this by:
Versioning: Each data entity has a version identifier, typically a timestamp or row version.
Read-Modify-Write Cycle: When a request retrieves data for update, it also retrieves the current version.
Update Attempt: The request modifies the data and includes the current version in the update request.
Server-side Validation: The server receives the update request and checks if the included version matches the current version in the database. If it matches, the update proceeds, and the version is incremented. If it doesn't match, it indicates a conflict, and the update is rejected.
Implementing OCC in ASP.NET Web API 2
To implement OCC in ASP.NET Web API 2, you can utilize the Entity Framework's concurrency token functionality. The following steps outline the process:
Enable Concurrency Token: In your Entity Framework configuration, enable concurrency tokens by setting the ConcurrencyMode
property of your DbContext to Fixed
. This will generate a concurrency token for each entity.
Attach Concurrency Token: In your API controller, when retrieving data for update, attach the concurrency token to the retrieved entity.
Include Concurrency Token in Update Request: When sending the update request, include the retrieved concurrency token along with the updated data.
Handle Concurrency Conflict: In your API controller, when handling the update request, check if the concurrency token in the update request matches the current version in the database. If it doesn't match, handle the concurrency conflict appropriately, such as returning a conflict error or prompting the user to refresh and retry.