/// <summary>
/// Writes the supplied <see cref="ISyndicationResource"/> to the specified <see cref="HttpContext"/> response stream and sets the appropriate headers.
/// </summary>
/// <param name="context">
/// An <see cref="HttpContext"/> object that provides references to the intrinsic server objects
/// (for example, <b>Request</b>, <b>Response</b>, <b>Session</b>, and <b>Server</b>) used to service HTTP requests.
/// </param>
/// <param name="resource">The <see cref="ISyndicationResource"/> to be written to the response stream.</param>
/// <exception cref="ArgumentNullException">The <paramref name="context"/> is a null reference (Nothing in Visual Basic).</exception>
/// <exception cref="ArgumentNullException">The <paramref name="resource"/> is a null reference (Nothing in Visual Basic).</exception>
private void WriteResource(HttpContext context, ISyndicationResource resource)
{
//------------------------------------------------------------
// Validate parameters
//------------------------------------------------------------
Guard.ArgumentNotNull(context, "context");
Guard.ArgumentNotNull(resource, "resource");
//------------------------------------------------------------
// Process conditional GET information if present
// (If conditions met, handler execution stops.)
//------------------------------------------------------------
SyndicationResourceHandler.ProcessConditionalGetInformation(context, resource);
//------------------------------------------------------------
// Modify response meta-data information
//------------------------------------------------------------
context.Response.ContentType = SyndicationResourceHandler.ContentFormatAsMimeType(resource.Format);
context.Response.AppendHeader("Content-Disposition", SyndicationResourceHandler.GetContentDisposition(resource.Format));
//------------------------------------------------------------
// Save XML representation of resource to output stream
//------------------------------------------------------------
SyndicationResourceSaveSettings settings = new SyndicationResourceSaveSettings();
settings.AutoDetectExtensions = true;
settings.MinimizeOutputSize = false;
resource.Save(context.Response.OutputStream, settings);
//------------------------------------------------------------
// Modify response caching expiration information
//------------------------------------------------------------
this.ModifyCacheExpiration(context);
}
/// <summary>
/// Enables a factory to reuse an existing HTTP handler instance.
/// </summary>
/// <param name="handler">The <see cref="IHttpHandler"/> object to reuse.</param>
public void ReleaseHandler(IHttpHandler handler)
{
//------------------------------------------------------------
// Local members
//------------------------------------------------------------
SyndicationResourceHandler syndicationHandler = null;
//------------------------------------------------------------
// Verify handler is reusable
//------------------------------------------------------------
if (handler.IsReusable)
{
lock (factoryHandlerLock)
{
if (factoryHandlers.Count < handlerPoolLimit)
{
syndicationHandler = handler as SyndicationResourceHandler;
if (syndicationHandler != null)
{
factoryHandlers.Push(syndicationHandler);
}
}
}
}
}
//============================================================
// PROTECTED METHODS
//============================================================
#region OnPreRender(EventArgs e)
/// <summary>
/// Raises the <see cref="Control.PreRender">PreRender</see> event.
/// </summary>
/// <param name="e">An <see cref="EventArgs"/> object that contains the event data.</param>
/// <remarks>
/// <para>This method notifies the server control to perform any necessary pre-rendering steps prior to saving view state and rendering content.</para>
/// <para>
/// During this step in the ASP.NET page life-cycle, the <see cref="SyndicationAutoDiscoveryHyperlink"/> will attempt to add
/// a <i><link rel="alternate" type="{MIME Type}" title="{Text}" href="{NavigateUrl}" /></i> to the page header section if
/// it is available to be modified.
/// </para>
/// <para>
/// The MIME media type of the link will be automatically selected based on the <see cref="Format">format</see>
/// unless the <see cref="MediaType">media type</see> has been explicitly specified.
/// </para>
/// <para>
/// The <i>title</i> attribute will only be rendered if the control's <see cref="Text"/> property has been specified.
/// </para>
/// </remarks>
protected override void OnPreRender(EventArgs e)
{
//------------------------------------------------------------
// Local members
//------------------------------------------------------------
string mimeType = String.Empty;
string href = String.Empty;
string title = String.Empty;
//------------------------------------------------------------
// Do not render control is invisible or disabled
//------------------------------------------------------------
if (!this.Visible || !this.Enabled)
{
base.OnPreRender(e);
return;
}
//------------------------------------------------------------
// As the page header control collection cannot be
// modified during the PreRender phase, exit this event
// handler to prevent raising an exception.
//------------------------------------------------------------
if (this.Parent is System.Web.UI.HtmlControls.HtmlHead)
{
base.OnPreRender(e);
return;
}
else if (this.Parent is System.Web.UI.WebControls.ContentPlaceHolder && this.Parent.Parent is System.Web.UI.HtmlControls.HtmlHead)
{
base.OnPreRender(e);
return;
}
//------------------------------------------------------------
// Render auto-discovery link
//------------------------------------------------------------
href = this.NavigateUrl != null?this.NavigateUrl.ToString() : String.Empty;
mimeType = SyndicationResourceHandler.ContentFormatAsMimeType(this.Format);
if (!String.IsNullOrEmpty(this.Text))
{
title = this.Text;
}
if (this.Page.Header != null)
{
string controlContent = String.Format(null, "\r\n<link rel=\"alternate\" type=\"{0}\" href=\"{1}\" />", mimeType, href);
if (!String.IsNullOrEmpty(title))
{
controlContent = String.Format(null, "\r\n<link rel=\"alternate\" type=\"{0}\" href=\"{1}\" title=\"{2}\" />", mimeType, href, title);
}
LiteralControl link = new LiteralControl(controlContent);
this.Page.Header.Controls.Add(link);
}
base.OnPreRender(e);
}
/// <summary>
/// Outputs server control content to a provided <see cref="HtmlTextWriter"/> object and stores tracing information about the control if tracing is enabled.
/// </summary>
/// <param name="writer">The <see cref="HtmlTextWriter"/> object that receives the control content.</param>
/// <remarks>
/// <para>
/// The MIME media type of the link will be automatically selected based on the <see cref="Format">format</see>
/// unless the <see cref="MediaType">media type</see> has been explicitly specified.
/// </para>
/// <para>
/// The <i>title</i> attribute will only be rendered if the control's <see cref="Text"/> property has been specified.
/// </para>
/// </remarks>
/// <exception cref="ArgumentNullException">The <paramref name="writer"/> is a null reference (Nothing in Visual Basic).</exception>
public override void RenderControl(HtmlTextWriter writer)
{
//------------------------------------------------------------
// Local members
//------------------------------------------------------------
string mimeType = String.Empty;
string href = String.Empty;
string title = String.Empty;
//------------------------------------------------------------
// Validate parameter
//------------------------------------------------------------
if (writer == null)
{
throw new ArgumentNullException("writer");
}
//------------------------------------------------------------
// Do not render control is invisible or disabled
//------------------------------------------------------------
if (!this.Enabled || !this.Visible)
{
return;
}
//------------------------------------------------------------
// Determine if link is positioned in HTML head
//------------------------------------------------------------
if (this.Parent is System.Web.UI.HtmlControls.HtmlHead)
{
//------------------------------------------------------------
// Render auto-discovery link
//------------------------------------------------------------
href = this.NavigateUrl != null?this.NavigateUrl.ToString() : String.Empty;
mimeType = SyndicationResourceHandler.ContentFormatAsMimeType(this.Format);
if (!String.IsNullOrEmpty(this.Text))
{
title = this.Text;
}
writer.AddAttribute(HtmlTextWriterAttribute.Rel, "alternate");
writer.AddAttribute(HtmlTextWriterAttribute.Type, mimeType);
writer.AddAttribute(HtmlTextWriterAttribute.Href, href);
if (!String.IsNullOrEmpty(title))
{
writer.AddAttribute(HtmlTextWriterAttribute.Title, title);
}
writer.RenderBeginTag(HtmlTextWriterTag.Link);
writer.RenderEndTag();
writer.WriteLine();
}
}
/// <summary>
/// Processes conditional GET header information for the supplied <see cref="ISyndicationResource"/>.
/// </summary>
/// <param name="context">
/// An <see cref="HttpContext"/> object that provides references to the intrinsic server objects
/// (for example, <b>Request</b>, <b>Response</b>, <b>Session</b>, and <b>Server</b>) used to service HTTP requests.
/// </param>
/// <param name="resource">The <see cref="ISyndicationResource"/> that is used when determining if conditional GET operation requirements were met.</param>
/// <remarks>
/// <para>
/// This method will retrieve conditional GET information from the request headers, and if present, will set the appropriate
/// response header information and status for the supplied <paramref name="resource"/>. If a modification date is available for
/// the supplied <paramref name="resource"/>, the conditional GET header information will be set so that clients may optionally
/// cache this infomration when making future requests.
/// </para>
/// <para>If a conditional GET operation was fulflled, no additional processing or modification of the response should be performed.</para>
/// </remarks>
/// <exception cref="ArgumentNullException">The <paramref name="context"/> is a null reference (Nothing in Visual Basic).</exception>
/// <exception cref="ArgumentNullException">The <paramref name="resource"/> is a null reference (Nothing in Visual Basic).</exception>
private static void ProcessConditionalGetInformation(HttpContext context, ISyndicationResource resource)
{
//------------------------------------------------------------
// Local members
//------------------------------------------------------------
string eTag = String.Empty;
string ifModifiedSince = String.Empty;
bool resourceIsUnmodified = false;
//------------------------------------------------------------
// Validate parameters
//------------------------------------------------------------
Guard.ArgumentNotNull(context, "context");
Guard.ArgumentNotNull(resource, "resource");
//------------------------------------------------------------
// Perform conditional GET processing
//------------------------------------------------------------
eTag = context.Request.Headers["If-None-Match"];
ifModifiedSince = context.Request.Headers["if-modified-since"];
if (!String.IsNullOrEmpty(eTag) || !String.IsNullOrEmpty(ifModifiedSince))
{
DateTime lastModified = SyndicationResourceHandler.GetLastModificationDate(resource);
if (lastModified == DateTime.MinValue)
{
return;
}
if (!String.IsNullOrEmpty(eTag))
{
//------------------------------------------------------------
// Determine if not modified by comparing last modified date-time
//------------------------------------------------------------
resourceIsUnmodified = eTag.Equals(lastModified.Ticks.ToString(CultureInfo.InvariantCulture));
}
else if (!String.IsNullOrEmpty(ifModifiedSince))
{
//------------------------------------------------------------
// Determine if not modified by comparing if modified since date-time
//------------------------------------------------------------
if (ifModifiedSince.IndexOf(";", StringComparison.OrdinalIgnoreCase) > -1)
{
ifModifiedSince = ifModifiedSince.Split(';').GetValue(0).ToString().Trim(); // Wed, 29 Dec 2004 18:34:27 GMT; length=126275
}
DateTime ifModifiedDate;
if (DateTime.TryParse(ifModifiedSince, out ifModifiedDate))
{
resourceIsUnmodified = (lastModified <= ifModifiedDate);
}
}
//------------------------------------------------------------
// Set conditional GET response information
//------------------------------------------------------------
if (resourceIsUnmodified)
{
context.Response.StatusCode = 304;
context.Response.SuppressContent = true;
context.Response.End(); // HTTP handler execution stops.
}
else
{
if (lastModified <= DateTime.Now)
{
context.Response.Cache.SetLastModified(lastModified);
}
else
{
context.Response.Cache.SetLastModified(context.Timestamp);
}
context.Response.Cache.SetETag(lastModified.Ticks.ToString(CultureInfo.InvariantCulture));
}
}
}
//============================================================
// PUBLIC METHODS
//============================================================
#region GetHandler(HttpContext context, string requestType, string url, string pathTranslated)
/// <summary>
/// Returns an instance of a class that implements the <see cref="IHttpHandler"/> interface.
/// </summary>
/// <param name="context">
/// An instance of the <see cref="HttpContext"/> class that provides references to
/// intrinsic server objects (for example, <b>Request</b>, <b>Response</b>, <b>Session</b>, and <b>Server</b>) used to service HTTP requests.
/// </param>
/// <param name="requestType">The HTTP data transfer method (<b>GET</b> or <b>POST</b>) that the client uses.</param>
/// <param name="url">The <see cref="HttpRequest.RawUrl">RawUrl</see> of the requested resource.</param>
/// <param name="pathTranslated">The <see cref="HttpRequest.PhysicalApplicationPath">PhysicalApplicationPath</see> to the requested resource.</param>
/// <returns>A new <see cref="SyndicationResourceHandler"/> object that processes the request.</returns>
/// <exception cref="ArgumentNullException">The <paramref name="context"/> is a null reference (Nothing in Visual Basic).</exception>
/// <exception cref="ArgumentNullException">The <paramref name="requestType"/> is a null reference (Nothing in Visual Basic).</exception>
/// <exception cref="ArgumentNullException">The <paramref name="requestType"/> is an empty string.</exception>
/// <exception cref="ArgumentNullException">The <paramref name="url"/> is a null reference (Nothing in Visual Basic).</exception>
/// <exception cref="ArgumentNullException">The <paramref name="url"/> is an empty string.</exception>
/// <exception cref="HttpException">The factory was unable to create a <see cref="SyndicationResourceHandler"/> for the request.</exception>
public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated)
{
//------------------------------------------------------------
// Local members
//------------------------------------------------------------
SyndicationResourceHandler handler = null;
//------------------------------------------------------------
// Validate parameters
//------------------------------------------------------------
Guard.ArgumentNotNull(context, "context");
Guard.ArgumentNotNullOrEmptyString(requestType, "requestType");
Guard.ArgumentNotNullOrEmptyString(url, "url");
//------------------------------------------------------------
// Return reusable handler if available
//------------------------------------------------------------
lock (factoryHandlerLock)
{
if (factoryHandlers.Count > 0)
{
handler = (SyndicationResourceHandler)factoryHandlers.Pop();
return(handler);
}
}
//------------------------------------------------------------
// Attempt to create handler
//------------------------------------------------------------
try
{
handler = (SyndicationResourceHandler)Activator.CreateInstance(typeof(SyndicationResourceHandler));
//------------------------------------------------------------
// Get factory name
//------------------------------------------------------------
string fullName = url.Substring(url.LastIndexOf('/') + 1);
string factoryName = fullName.Substring(0, fullName.IndexOf('.'));
//------------------------------------------------------------
// Set syndication format of handler based on factory path
//------------------------------------------------------------
if (String.Compare(factoryName, "Apml", StringComparison.OrdinalIgnoreCase) == 0)
{
handler.Format = SyndicationContentFormat.Apml;
}
else if (String.Compare(factoryName, "Atom", StringComparison.OrdinalIgnoreCase) == 0)
{
handler.Format = SyndicationContentFormat.Atom;
}
else if (String.Compare(factoryName, "BlogML", StringComparison.OrdinalIgnoreCase) == 0)
{
handler.Format = SyndicationContentFormat.BlogML;
}
else if (String.Compare(factoryName, "Opml", StringComparison.OrdinalIgnoreCase) == 0)
{
handler.Format = SyndicationContentFormat.Opml;
}
else if (String.Compare(factoryName, "Rsd", StringComparison.OrdinalIgnoreCase) == 0)
{
handler.Format = SyndicationContentFormat.Rsd;
}
else if (String.Compare(factoryName, "Rss", StringComparison.OrdinalIgnoreCase) == 0)
{
handler.Format = SyndicationContentFormat.Rss;
}
return(handler);
}
catch (Exception exception)
{
//------------------------------------------------------------
// Rethrow exception as HttpException with param information
//------------------------------------------------------------
throw new HttpException(String.Format(null, "The SyndicationHttpHandlerFactory was unable to create a handler for requestType='{0}', url='{1}', pathTranslated='{2}'.", requestType, url, pathTranslated), exception);
}
}
