reactiveui/refit · error · ArgumentException

Response must have an associated request message.

Error message

Response must have an associated request message.

What it means

Thrown by the ApiResponse<T> constructor when the supplied HttpResponseMessage is non-null but its RequestMessage property is null. ApiResponse requires a request to be associated (it exposes RequestMessage and uses it for error construction), so a response detached from its request is rejected.

Source

Thrown at src/Refit/ApiResponse{T}.cs:58

        RefitSettings settings)
        : this(response, content, settings, null)
    {
    }

    /// <summary>Initializes a new instance of the <see cref="ApiResponse{T}"/> class.</summary>
    /// <param name="response">Original HTTP Response message.</param>
    /// <param name="content">Response content.</param>
    /// <param name="settings">Refit settings used to send the request.</param>
    /// <param name="error">The exception, if the request failed.</param>
    /// <exception cref="ArgumentNullException">Thrown when <paramref name="response"/> is <c>null</c>.</exception>
    public ApiResponse(
        HttpResponseMessage response,
        T? content,
        RefitSettings settings,
        ApiExceptionBase? error)
        : this(
            (response ?? throw new ArgumentNullException(nameof(response))).RequestMessage
            ?? throw new ArgumentException(
                "Response must have an associated request message.",
                nameof(response)),
            response,
            content,
            settings,
            error)
    {
    }

    /// <summary>Gets the deserialized request content as <typeparamref name="T"/>.</summary>
    public T? Content { get; } = content;

    /// <summary>Gets a value indicating whether deserialized <see cref="Content"/> is available.</summary>
    [MemberNotNullWhen(true, nameof(Content))]
    public bool HasContent => Content is not null;

    /// <summary>Gets a value indicating whether the request was successful and deserialized <see cref="Content"/> is available.</summary>
    [MemberNotNullWhen(true, nameof(Content))]

View on GitHub (pinned to b455f65ecc)

Solutions

1. Set response.RequestMessage = request on any HttpResponseMessage you construct before passing it to ApiResponse.
2. In a custom DelegatingHandler, always set RequestMessage on the response you return (or call base.SendAsync which sets it).
3. In tests, use a helper that clones the request reference onto the response.

Example fix

// before
var resp = new HttpResponseMessage(HttpStatusCode.OK) { Content = ... };
var api = new ApiResponse<MyDto>(resp, dto, settings, null); // throws

// after
var resp = new HttpResponseMessage(HttpStatusCode.OK) { Content = ... };
resp.RequestMessage = requestMsg;
var api = new ApiResponse<MyDto>(resp, dto, settings, null);

// Ensure any manually constructed response carries its request.
static HttpResponseMessage WithRequest(HttpResponseMessage resp, HttpRequestMessage req)
{
    resp.RequestMessage = req ?? throw new ArgumentNullException(nameof(req));
    return resp;
}

When it happens

Trigger: Constructing `new ApiResponse<T>(response, ...)` where response.RequestMessage was never set — most commonly a hand-built HttpResponseMessage in a test or a custom HttpMessageHandler that creates responses without linking them to the request.

Common situations: Unit tests that new up HttpResponseMessage(OK) without setting .RequestMessage; custom handlers/delegating handlers that return fresh responses; mocking frameworks that produce responses missing the back-reference.

Related errors

• The HttpResponseMessage has no associated RequestMessage. Wh
• URL path {relativePath} must not contain CR or LF characters
• Response is successful, cannot create an ApiException.
• The response is unavailable for this API response.
• The [Url] parameter value "{value}" must be an absolute URI

AI-assisted analysis of reactiveui/refit@b455f65ecc (2026-08-13). Data as JSON: /api/errors/85ee6c3e138c627e. Report an issue: GitHub.