Web API return csv file

I need to get a csv file from web api controller. I can not get "Save As" dialog to show up. Only text output shows up on the page. I tried both, calling Export from jquery and also plain old html

Controller:

[System.Web.Http.HttpGet]
public HttpResponseMessage Export()
{
    StringBuilder sb = new StringBuilder();
    IEnumerable<CustomerDiscount> list = this.subscriberRepository.GetSubscribers();

    foreach (CustomerDiscount item in list)
    {
        sb.AppendFormat(
            "{0};{1};{2};",
            item.CustomerName,
            item.CustomerNumber,
            Environment.NewLine);
    }

    MemoryStream stream = new MemoryStream();
    StreamWriter writer = new StreamWriter(stream);
    writer.Write(sb.ToString());
    writer.Flush();
    stream.Position = 0;

    HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
    result.Content = new StreamContent(stream);
    result.Content.Headers.ContentType =
        new MediaTypeHeaderValue("text/csv");
    result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = "Export.csv" };
    return result;
}

EDIT: added this line:

result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = "Export.csv" };

still doesn't work

I call it like this:

<a id="export" href="/Relay/Billing/Export" class="btn btn-primary">Export</a>

and also tried it like this:

$("#export").click(function () {
    $.post("/Relay/Billing/Export", { type: $("#discountType").val() })
      .done(function (data) {
      });
});

Still no Save As box

I do not know whether this is proper protocol but this is how I did it before. So you have a web page from which you will invoke an API that will response with the file and it should be handled by browser's save as dialog.

The HTML:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>

    <script type="text/javascript">
        function save() {
            window.open('http://localhost:45719/api/home?id=12', '_blank', '');
        }
    </script>
</head>
<body>
    <a class="btn btn-primary" onclick="save()">Export</a>
</body>
</html>

The action:

public HttpResponseMessage Get(int id)
{
    MemoryStream stream = new MemoryStream();
    StreamWriter writer = new StreamWriter(stream);
    writer.Write("Hello, World!");
    writer.Flush();
    stream.Position = 0;

    HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
    result.Content = new StreamContent(stream);
    result.Content.Headers.ContentType = new MediaTypeHeaderValue("text/csv");
    result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = "Export.csv" };
    return result;
}

This is working for me in both Chrome and Firefox latest.