How to set downloading file name in ASP.NET Web API

In my ApiController class, I have following method to download a file created by server.

public HttpResponseMessage Get(int id)
{
    try
    {
        string dir = HttpContext.Current.Server.MapPath("~"); //location of the template file
        Stream file = new MemoryStream();
        Stream result = _service.GetMyForm(id, dir, file);
        if (result == null)
        {
            return Request.CreateResponse(HttpStatusCode.NotFound);
        }
        result.Position = 0;
        HttpResponseMessage response = new HttpResponseMessage();
        response.StatusCode = HttpStatusCode.OK;
        response.Content = new StreamContent(result);
        return response;
    }
    catch (IOException)
    {
        return Request.CreateResponse(HttpStatusCode.InternalServerError);
    }
}

Everything is working perfect except that default downloading file name is its id so user might have to type his/her own file name at save as dialog each time. Is there any way to set a default file name in the code above?

Solution 1:

You need to set the Content-Disposition header on the HttpResponseMessage:

HttpResponseMessage response = new HttpResponseMessage();
response.StatusCode = HttpStatusCode.OK;
response.Content = new StreamContent(result);
response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
{
    FileName = "foo.txt"
};

Solution 2:

EDIT: As mentioned in a comment, My answer doesn't account for characters that need to be escaped like a ;. You should use the accepted answer Darin made if your file name could contain a semi-colon.

Add a Response.AddHeader to set the file name

Response.AddHeader("Content-Disposition", "attachment; filename=*FILE_NAME*");

Just change FILE_NAME to the name of the file.

Solution 3:

If you want to ensure that the file name is properly encoded but also avoid the WebApi HttpResponseMessage you can use the following:

Response.AddHeader("Content-Disposition", new System.Net.Mime.ContentDisposition("attachment") { FileName = "foo.txt" }.ToString());

You may use either ContentDisposition or ContentDispositionHeaderValue. Calling ToString on an instance of either will do the encoding of file names for you.