I have a C# Entity Framework Web API 2 controller. Currently when an attempt is made via the POST method to create an object with the same text for the main text field, I return a 409 Conflict error as an StatusCode result to indicate the addition is considered a duplicate.
What I'd like to do is return the server side object that triggered the duplicate error too. So I need something akin to the Ok() method but a variant that returns a 409 Conflict error as the HTTP status code instead of an HTTP OK status code.
Is there such a thing? How can I do this? If I can make this work the client doesn't have to do a subsequent Get call to the server to get the existing object after receiving a 409 Conflict error.
Here's the current POST method:
public IHttpActionResult PostCanonical(Canonical canonical)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
// Check for duplicate Canonical text for the same app name.
if (db.IsDuplicateCanonical(canonical.AppName, canonical.Text))
{
// It's a duplicate. Return an HTTP 409 Conflict error to let the client know.
return StatusCode(HttpStatusCode.Conflict);
}
db.CanonicalSentences.Add(canonical);
db.SaveChanges();
return CreatedAtRoute("DefaultApi", new { id = canonical.ID }, canonical);
}
EDIT: This solution is for WebApi prior v5, please see this answer if you are using v5 or above.
You could return a NegotiatedContentResult<T>
that lets you specify the status code and an object to be put into the http message body.
Change your code to something like this:
public IHttpActionResult PostCanonical(Canonical canonical)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
// Check for duplicate Canonical text for the same app name.
if (db.IsDuplicateCanonical(canonical.AppName, canonical.Text))
{
// It's a duplicate. Return an HTTP 409 Conflict error to let the client know.
var original = db.CanonicalSentences.First(c => c.ID == canonical.ID);
return new NegotiatedContentResult<T>(HttpStatusCode.Conflict, original, this);
}
db.CanonicalSentences.Add(canonical);
db.SaveChanges();
return CreatedAtRoute("DefaultApi", new { id = canonical.ID }, canonical);
}
Or maybe wrap it an extension method like this:
public static class HttpActionResultExtensions {
public static IHttpActionResult StatusCodeWithContent<T>(this ApiController @this, HttpStatusCode statusCode, T content) {
return new NegotiatedContentResult<T>(statusCode, content, @this);
}
}
And then use the extension like this:
public IHttpActionResult PostCanonical(Canonical canonical)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
// Check for duplicate Canonical text for the same app name.
if (db.IsDuplicateCanonical(canonical.AppName, canonical.Text))
{
// It's a duplicate. Return an HTTP 409 Conflict error to let the client know.
var original = db.CanonicalSentences.First(c => c.ID == canonical.ID);
return StatusCodeWithContent(HttpStatusCode.Conflict, original)
}
db.CanonicalSentences.Add(canonical);
db.SaveChanges();
return CreatedAtRoute("DefaultApi", new { id = canonical.ID }, canonical);
}
You should return Content:
return Content(HttpStatusCode.Conflict, original);
Content
is method on the ApiController
class which will create a NegotiatedContentResult
with the provided HttpStatusCode
and content. There is no need to create your own extension method on the ApiController class like in the accepted answer.