/// <summary>
/// Adds the correct response headers for a file download request.
/// </summary>
/// <param name="context">HttpContext</param>
/// <param name="fileHeadObject">The file object representing the file to stream.</param>
public static void AddDownloadHeaders(HttpContext context, FileHeadObject fileHeadObject)
{
HttpContext httpContext = context as HttpContext;
string requestLanguage = string.Empty;
if (httpContext.Request.UserLanguages.Length > 0)
requestLanguage = httpContext.Request.UserLanguages[0];
httpContext.Response.AppendHeader("Content-Length", fileHeadObject.BytesCount.ToString(CultureInfo.InvariantCulture));
httpContext.Response.ContentType = GetMimeType(fileHeadObject.FileName);
string disposition = BuildContentDispositionHeader(fileHeadObject, requestLanguage,
httpContext.Request.Browser.Type,
httpContext.Request.Browser.MajorVersion,
httpContext.Request.Browser.Platform);
httpContext.Response.AppendHeader("Content-Disposition", disposition); // gives save-as dialog and filename
}
private static string TruncateHeaderLine(FileHeadObject fileHeadObject, string text, int firstLineLen)
{
int maxLen = firstLineLen;
int pos = 0;
if (pos + maxLen < text.Length)
{
int lastByteCount = 0;
while (pos < maxLen)
{
if (text[pos] == '%') // we don't want a filename to end with '%'.
lastByteCount = 3;
else
lastByteCount = 1;
pos += lastByteCount;
}
pos = pos - lastByteCount;
string ext = fileHeadObject.FileExtensionName;
text = text.Substring(0, pos);
int dotPos = text.LastIndexOf(".", StringComparison.Ordinal);
if (dotPos > 0)
text = text.Substring(0, dotPos);
text += ext;
}
return text;
}
/// <summary>
/// If the filename contains high ASCII and client is non-English, the filename to use (w/o extension).
/// </summary>
/// <param name="fileHeadObject"></param>
private static string GetPlaceholderFileName(FileHeadObject fileHeadObject)
{
return string.Format(CultureInfo.InvariantCulture, "Download_{0}", fileHeadObject.Id.ToString());
}
private static string GetDownloadFilename(FileHeadObject fileHeadObject, string userLanguage, bool requestIsFromXPIE6Japanese)
{
bool isUsePlaceholder = false;
string origFileName = fileHeadObject.FileName;
string fileName;
// if the request from WINXP IE6 and Japanese
if (requestIsFromXPIE6Japanese)
{
fileName = BuildDownloadNameForXPIE6Japanese(fileHeadObject);
}
else
{
if (StringContainsHighAscii(origFileName))
{
isUsePlaceholder = true;
if (userLanguage.StartsWith("en", StringComparison.OrdinalIgnoreCase))
isUsePlaceholder = false;
}
string nameToUse = origFileName;
if (isUsePlaceholder)
{
string extension = fileHeadObject.FileExtensionName;
nameToUse = GetPlaceholderFileName(fileHeadObject) + extension;
}
fileName = HttpUtility.UrlPathEncode(nameToUse);
fileName = fileName.Replace("#", "%23");
}
return fileName;
}
/// <summary>
/// Builds the optimum file name that can be displayed without exceeeding
/// header limit.
/// </summary>
/// <param name="fileHeadObject">original file head</param>
/// <returns></returns>
private static string BuildDownloadNameForXPIE6Japanese(FileHeadObject fileHeadObject)
{
//To DO Krishna: We can change this logic to use ability of UTF8 encoded byte to determine the truncation point.
string nameToUse = fileHeadObject.FileName;
string ext = fileHeadObject.FileExtensionName;
if (ext.Length > 0)
nameToUse = nameToUse.Substring(0, nameToUse.Length - ext.Length);
char[] charArr = nameToUse.ToCharArray();
string holderStr;
StringBuilder fileName = new StringBuilder();
int nCurrentLength = 0;
foreach (char c in charArr)
{
holderStr = HttpUtility.UrlEncode(c.ToString());
if ((holderStr.Length + nCurrentLength) > 155)
break;
nCurrentLength += holderStr.Length;
fileName.Append(holderStr);
holderStr = null;
}
if (ext.Length > 0)
fileName.Append(ext);
return fileName.ToString();
}
/// <summary>
/// Note that the httpContext param can legally be null. See callers.
/// </summary>
/// <remarks>
/// The Content-Disposition HTTP response header gives us some control over how the client will react
/// to the file download. In particular, whether or not the client will launch a "Save As" dialog when a file
/// is requested for dowload. See RFC 1806 for detials.</remarks>
/// <remarks>We tried excluding "attachment" from the contentDisposition header for IE 5.5 to avoid
/// getting a double download prompt. Except, this causes a problem for the case
/// where Office2K is installed on IE5.5 -- for that case we don't get any download prompt
/// unless we have the header. So on IE5.5 we get a double download prompt.
/// </remarks>
/// <param name="fileHeadObject"></param>
/// <param name="userLanguage"></param>
/// <param name="capabilitiesType"></param>
/// <param name="majorVersion"></param>
/// <param name="platform"></param>
/// <returns></returns>
private static string BuildContentDispositionHeader(FileHeadObject fileHeadObject, string userLanguage, string capabilitiesType, int majorVersion, string platform)
{
// To build and hold the Content-Disposition header.
StringBuilder dispositionBuilder = new StringBuilder();
dispositionBuilder.Append("attachment;");
// Note that we cannot determine browser details from a WebOperationContext,
// so we simply ignore this check in that case. See callers.
bool requestIsFromXPIE6Japanese = false;
if ((!string.IsNullOrEmpty(capabilitiesType)) && majorVersion > -1 && (!string.IsNullOrEmpty(platform)))
requestIsFromXPIE6Japanese = IfRequestIsFromXPIE6Japanese(userLanguage, capabilitiesType, majorVersion, platform);
dispositionBuilder.AppendFormat("filename=\"{0}\"", GetDownloadFilename(fileHeadObject, userLanguage, requestIsFromXPIE6Japanese));
string disposition = dispositionBuilder.ToString();
// Max line length is 78 characters, including header name; we'll limit the first line to less characters
// to make sure we have space for the header and the line terminators
if (!requestIsFromXPIE6Japanese)
disposition = TruncateHeaderLine(fileHeadObject, disposition, 100);
return disposition;
}
