modify SPListItem fields with vars from the Session in the itemAdding or itemAdded events

Yesterday, a colleague of me and I tried to alter a field of a SPListItem right after the moment that the item has been created. We stored a var in the sessionState and tried to read that one, so we could use that variable to alter the newly created SPListItem.

We found out that this was not as easy as we thought.

When using the itemAdded event, the httpContext is not available, so it's not possible to get the vars out of the HttpContext.Current.Session

When using the itemAdding event, the HttpContext is available, but the properties.ListItem is null then. This is expected behaviour, because the SPListItem is only filled with data from the database and in the itemAdding event, no write actions to the database have been executed yet.

In this case, the properties.AfterProperties can be used to modify a field on creation.

below is an example that shows whether the HttpContext and properties.ListItem are null or not shows how to modify properties when an item is added.



<br />public class ItemEventReceiver : SPItemEventReceiver<br />{<br /> private HttpContext hContext;<br /><br /> public ItemEventReceiver()<br /> {<br /> hContext = HttpContext.Current;<br /> }<br /> public override void ItemAdded(SPItemEventProperties properties)<br /> {<br /> Debug.WriteLine("ItemAdded");<br /> CheckHContextAndSPListItem(properties.ListItem);<br /> base.ItemAdded(properties);<br /> }<br /><br /> /// <summary><br /> /// overrides the standard ItemAdding. In this case<br /> /// </summary><br /> /// <param name="properties"></param><br /> public override void ItemAdding(SPItemEventProperties properties)<br /> {<br /><br /> string internalFieldName = null;<br /> string FIELD_NAME = "Foo"; <br /> SPFieldLookupValue lookupField = null;<br /> <br /> Debug.WriteLine("ItemAdding");<br /> CheckHContextAndSPListItem(properties.ListItem);<br /><br /> using (SPWeb web = properties.OpenWeb())<br /> {<br /> internalFieldName = web.Lists[properties.ListId].Fields[FIELD_NAME].InternalName;<br /> }<br /><br /> // example for adding a SPFieldLookupValue to a SPFieldLookup<br /> lookupField = new SPFieldLookupValue(1, hContext.Session["key"].ToString());<br /> string tempValue = lookupField.ToString();<br /> properties.AfterProperties[internalFieldName] = tempValue;<br /><br /> }<br /><br /> /// <summary><br /> /// checks the values of hContext and SPListItem<br /> /// </summary><br /> /// <param name="sPListItem">SPListItem out of the SPItemEventProperties</param><br /> private void CheckHContextAndSPListItem(SPListItem listItem)<br /> {<br /> if (hContext == null)<br /> {<br /> Debug.WriteLine("hContext is null");<br /> }<br /><br /> if (listItem == null)<br /> {<br /> Debug.WriteLine("listItem is null");<br /> }<br /><br /> }<br /><br /><br />}