Duplicate headers received from server

The server SHOULD put double quotes around the filename, as mentioned by @cusman and @Touko in their replies.

For example:

Response.AddHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");

This ones a little old but was high in the google ranking so I thought I would throw in the answer I found from Chrome, pdf display, Duplicate headers received from the server

Basically my problem also was that the filename contained commas. Do a replace on commas to remove them and you should be fine. My function to make a valid filename is below.

    public static string MakeValidFileName(string name)
    {
        string invalidChars = Regex.Escape(new string(System.IO.Path.GetInvalidFileNameChars()));
        string invalidReStr = string.Format(@"[{0}]+", invalidChars);
        string replace = Regex.Replace(name, invalidReStr, "_").Replace(";", "").Replace(",", "");
        return replace;
    }

Just put a pair of double quotes around your file name like this:

this.Response.AddHeader("Content-disposition", $"attachment; filename=\"{outputFileName}\"");