Sebastian's Blog

Hello!

I was faced with a small problem the other day. In an external database the url to a content item, such as a document, discussion thread or a wiki page, was to be stored in several parts; the url to site, the url to the list and finally the url to the list item.
The easy part was the site and the item urls since the come out of the SPItemEventProperty of the event handler I was working in. But when it came to the list, it was something different. I.e. the user can change the Title of the list and therefore the title cannot be used. There are several ways of doing this, but the way I choose was this method;
First, get the value of the field named "Encoded Absolute URL" which out of the SPItemEventProperty.ListItem. This url is the exact url SharePoint will use when a user click on a link for that item.
Decoding and encoding this url is necessary for what I did next, taking the substring of this url and removing the site url and the item url will get you the url for the list.
Below is a code example of what I did;

                /* First, encode the property from the event handler */
                string siteUrl = SPEncode.UrlEncodeAsUrl(properties.WebUrl);

                /* Next, get the absolute url from the ListItem property and decode at the same time*/
                string absoluteItemUrl = SPEncode.UrlDecodeAsUrl(properties.ListItem["Encoded Absolute URL"].ToString());

                /* Encode the url to get the absolute url in the same encoding as the web url */
                absoluteItemUrl = SPEncode.UrlEncodeAsUrl(absoluteItemUrl);

                /* Next, get the substrings to leave only the list url */

                string temp = absoluteItemUrl.Substring(siteUrl.Length);
                string tempUrl = temp.Substring(0, temp.LastIndexOf('/') + 1);

Hi!

I was presented with a problem while working at a customer of mine. When running event handlers, specially ItemUpdated, the code might be run several times by different threads. The thing is that the eventhandler makes some changes to the list item that generates an error if the code is run again. That is to say that the name of the item changes in the eventhandler. The problem consists of making sure that the code is only run once.

To solve this problem, I used a hashtable to store a temporary variable. Using a hashtable has the advantage that once the variable is set in the hastable, a try/catch loop will sort out the following threads since the hastable will generate an error if trying to insert duplicates.

Thus, when an error is received from the hashtable, a return statement is set, allowing only the first thread to run the code. Once the code is run, don't forget to reset the hashtable.

Since Gustaf, a colluege of mine, come up with the original idea, here is a link to his blog, also with code examples. http://gustafwesterlund.blogspot.com/2007/08/how-to-stop-infinite-recursionsloops-in.html

//Sebastian