Unicode in Content-Disposition header

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I had similar problem. You have to use HttpUtility.UrlEncode or Server.UrlEncode to encode filename. Also I remember firefox didn’t need it. Moreoverit ruined filename when it’s url-encoded. My code:

// IE needs url encoding, FF doesn't support it, Google Chrome doesn't care
if (Request.Browser.IsBrowser ("IE"))
{
    fileName = Server.UrlEncode(fileName);
}

Response.Clear ();
Response.AddHeader ("content-disposition", String.Format ("attachment;filename=\"{0}\"", fileName));
Response.AddHeader ("Content-Length", data.Length.ToString (CultureInfo.InvariantCulture));
Response.ContentType = mimeType;
Response.BinaryWrite(data);

Edit

I have read specification more carefully. First of all RFC2183 states that:

Current [RFC 2045] grammar restricts parameter values (and hence Content-Disposition filenames) to US-ASCII.

But then I found references that [RFC 2045] is absolete and one must reference RFC 2231, which states:

Asterisks (“*”) are reused to provide
the indicator that language and
character set information is present
and encoding is being used. A single
quote (“‘”) is used to delimit the
character set and language information
at the beginning of the parameter
value. Percent signs (“%”) are used as
the encoding flag, which agrees with
RFC 2047.

Which means that you can use UrlEncode for non-ascii symbols, as long as you include the encoding as stated in the rfc. Here is an example:

string.Format("attachment; filename=\"{0}\"; filename*=UTF-8''{0}", Server.UrlEncode(fileName, Encoding.UTF8));

Note that filename is included in addition to filename* for backwards compatibility. You can also choose another encoding and modify the parameter accordingly, but UTF-8 covers everything.

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