Generating Unique IDs in Windows SharePoint

In many scenarios, it is useful to have a system-generated unique identifier for all items contained within a site. For example, you may wish to create a unique identifier for all records submitted to the Records Center. Regardless of which library that the record is stored, each record contained within the site has a unique identifier. SharePoint generates an ID for each item in a list, but these ID's are repeated in each list or library and are not unique across the site. Internally SharePoint creates a unique GUID for each item, but it is not exposed to the end user, and even if it were, GUID's are not very user-friendly.

Implementation of our unique ID includes a list for maintaining the value, and an event handler for retrieving and setting the value.

private static int GetUniqueId(SPWeb web)
        {
            int returnValue = -1;
            int retryCounter = 0;
            int uniqueId = -1;

      
            try
            {
                // Get the list and list item
                SPList list = web.Lists["Counter"];
                SPListItem item = list.Items[0];

                // Get the value for the unique id
                uniqueId = int.Parse(item["Title"].ToString());
                
                // Increment and update the value
                item["Title"] = uniqueId + 1;
                item.Update();
                
                // Set the value to return
                returnValue = uniqueId;
            }
            catch (Exception ex)
            {
                // Handle the exception by retrying 5 times
                retryCounter += 1;
                if (retryCounter <= 5)
                {
                    System.Threading.Thread.Sleep(2500);
                    goto ReTry;
                }
                else
                {
                    // Write the exception to the log
                }
            }
            return returnValue;
        }

 public override void ItemAdding(SPItemEventProperties properties)
        {
            base.DisableEventFiring();
            try
            {
                using (SPWeb web = properties.OpenWeb())
                {
                    // Set the unique id value on the item
                    properties.AfterProperties["MyUniqueId"] = GetUniqueId(web);
                }
            }
            catch (Exception ex)
            { }
            finally
            {   base.EnableEventFiring();   }
            base.ItemAdding(properties);
        }