ItemAdded event handler vs. ItemAdding event handler

I often get asked this question when should i use the ItemAdded / ItemAdding event handler in MOSS 2007. Well the answer is really simple. If you are adding an item to a list and want to perform a set of actions before the item is saved, including preventing the item from being saved or throw an exception, "ItemAdding" is the event handler to override. If you want to perform post add actions then "ItemAdded" in the event handler to override.

Also note that in your event handler code, you would need to use the "AfterProperties" bag to read the list field values that have changed (as opposed to the "Properties" bag). For example:


private void VowelCheck(SPItemEventProperties properties)
{
string vowelErrorMessage = string.Empty;
// Check whether the Title field exists within the List
if (properties.AfterProperties["Title"] != null)
{
// Assumption that you have a class called VowelListManager.cs which has a function CheckVowelExists()
vowelErrorMessage = VowelListManager.CheckVowelExists(properties.AfterProperties["Title"].ToString());
}

// If Error Message is returned then the current words has failed the vowel test- This code also shows how to cancel a SharePoint event (like stop the item from being added or updated)
if (!vowelErrorMessage.Equals(string.Empty))
{
properties.ErrorMessage = vowelErrorMessage;
properties.Cancel = true;
}
}