Edit

ActionResult<T> sets StatusCode to 200

  • Article

When returning a T in an MVC/API controller action that declares the return type as ActionResult<TValue>, the ObjectResult.StatusCode is always set to 200, except when the T is a ProblemDetails.

This change can cause unexpected behavior in some scenarios where you set the status code manually, since previously the ObjectResult.StatusCode was null. Also, an action filter could be affected by this change if it expects a null value instead of 200.

Version introduced

ASP.NET Core 6.0

Previous behavior

Previously, a controller's action that returns T and sets Response.StatusCode manually generated the specified response status code. For example, the following controller's action will generate a 202 Accepted response.

// Generates a 202 Accepted response
public ActionResult<Model> Get()
{
    Response.StatusCode = StatusCodes.Status202Accepted;
    return new Model();
}

New behavior

Now, the same controller's action that returns T and sets Response.StatusCode manually always generates a 200 OK response.

// Generates a 200 OK response
public ActionResult<Model> Get()
{
    Response.StatusCode = StatusCodes.Status202Accepted;
    return new Model();
}

Type of breaking change

This change can affect source compatibility.

Reason for change

Returning a status code of 200 OK is documented since ASP.NET Core 3.1. However, it keeps StatusCode as null and eventually generates a 200 OK response only because it's the default. Since the default internal behavior could change, we decided to avoid relying on the default and to explicitly set StatusCode to the expected 200 OK.

If your code sets the status code manually and is broken by this change, you'll need to change your controller action. For example, the following code snippet sets a status code of 202 and is broken by this change.

public ActionResult<Model> Get()
{
    Response.StatusCode = StatusCodes.Status202Accepted;
    return new Model();
}

To retain the desired behavior of a 202 status code, the following code snippets show some options.

public ActionResult<Model> Get()
{
   return Accepted(new Model());
}

// or

public ActionResult<Model> Get()
{
   return StatusCode(StatusCodes.Status202Accepted, new Model());
}

// or

public Model Get()
{
   Response.StatusCode = StatusCodes.Status202Accepted;
   return new Model();
}

Affected APIs

  • MVC/API controller actions

See also