Recently I developed an RSS Reader webpart which would take the RSS URL of list to render its feeds. Very much same like the out of the box webpart with the exception that it was AJAX enabled. I would post the details of that part on the blog when I am finished.
An idea came to me that wouldn’t it be nice to also enable users to just give the list URL rather than RSS URL since would reduce the few steps on the user’s side. I thought it would be just a matter of accessing the RssUrl property of SPList object, but to my surprise it was not to be. There is no property such property in the API, so I decided to write my own function for it.
Let’s analyze the RSS URL of a list or a library. Whenever the user clicks on View RSS feed on a library, here is how SharePoint constructs the URL:
http://<server>/<site>/_layouts/listfeed.aspx?List=%7B14206B18%2DF68F%2D479B%2DBC84%2D15EE48D19D7D%7D
Listfeed.aspx is the inbuilt RSS viewer of sharepoint which accepts a parameter which is the GUID of the list. %2D tokens refer to ‘-‘characters which exist inside the GUID. Considering all this, it’s easy to write a function which will return the RSS URL. Here is the code for the same:
private string MakeRssUrl(string rawurl)
{
try
{
Uri url = new Uri(rawurl, UriKind.Absolute);
if (url.GetLeftPart(UriPartial.Path).Contains(“_layouts/listfeed.aspx”))
{
return rawurl;
}
else
{
string rssurl;
using (SPWeb web = new SPSite(rawurl).OpenWeb())
{
SPList list = web.GetListFromUrl(rawurl);
rssurl = web.Url + "/_layouts/listfeed.aspx?list=" + list.ID;
return rssurl;
}
}
}
catch (UriFormatException e)
{
return string.Empty;
}
}
The code is pretty self explanatory. The argument to function is list URL or RSS url. We first check if the URL is RSS URL itself, and if it is we just return. Otherwise, if it’s a list URL, we create a SPList instance, grap the GUID and contatenate it with the site URL and listfeed.aspx.
Note that the function does not validate if the given URL was actually a valid list URL or not. The exception handling for that case should be left to the caller of the function.
