HttpClient.PostAsync response.Content.Headers.ContentDisposition is null

Question

I've created an Azure Function project (.NET Framework Isolated v4)

    [Function("Function1")]
    public HttpResponseData Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequestData req)
    {
        _logger.LogInformation("C# HTTP trigger function processed a request.");

        var response = req.CreateResponse(HttpStatusCode.OK);

        response.Headers.Add("Content-Type", "text/plain; charset=utf-8");
        response.Headers.Add("Content-Disposition", $@"attachment; filename=""MyFile.txt""");
        response.WriteString("test contents");

        return response;
    }

Then a Blazor WASM .NET 7.0 project, modifying the FetchData page as follows:

    protected override async Task OnInitializedAsync()
{
    var content = new StringContent("");

    var response = await Http.PostAsync("http://localhost:7155/api/Function1", content);

    if (response.IsSuccessStatusCode)
    {
        var contentDispositionHeader = response.Content.Headers.ContentDisposition;
        if (contentDispositionHeader != null)
        {
            Console.WriteLine($"Content-Disposition: {contentDispositionHeader.ToString()}");
        }
    }
}

However, response.Content.Headers.ContentDisposition is always null.

Fiddler shows the headers including:

Content-Disposition: attachment; filename="MyFile.txt"

What is stopping HttpResponseMessage from receiving ContentDisposition?

Answer 1

Solution is to add:

      response.Headers.Add("Access-Control-Expose-Headers", "*");