updating fields via SharePoint Form and via List item event receiver - sharepoint-2010

Question

I am confused and cannot seem to find the right answer to this problem:
When I use the ItemUpdating method in the event receiver to update the field title as show in the code below it works, but other fields which I have changed via the "Edit Form" do not change. they remain as they are.
public override void ItemUpdating(SPItemEventProperties properties)
{
SPListitem item = properties.ListItem;
item["Title"] = "title has been changed";
item.Update();
}
if I put the above code in ItemUpdated it does not work, but the changes done via UI (edit form) take effect.
can anyone help me solve this problem?
thank you
Editing
Let me put it simply like this:
can anyone tell me how can I update one or multiple fields via Event Receiver and the other field(s) via the Edit Form of a list?
I hope this is clearer.

Answer 1

It is always best to use ItemUpdated in the event receiver to update a field in the list.
and also you must note that updating the field in the event receiver using
item.Update();
might cause some problems when you start workflow. You can use the following
ways to update multiple field.
base.EventFiringEnabled = false;
try
{
item.SystemUpdate(false);
}
finally
{
base.EventFiringEnabled = true;
}
break;

Answer 2

When using the ItemUpdating event, check the AfterProperties property of the properties parameter. It is a dictionary containing all the new values that the item will have. It contains raw values, though, all of them as strings, before being processed into the actual values you'll see when you fetch the item properties.
When you execute your code in the ItemUpdating event, what happens is this:
User clicks save;
ItemUpdating is fired and executes up to your call to Update().
At this point, your call to Update() fires another ItemUpdating event to the item. In the context it runs, no fields have changed other than Title.
Control returns to the method you overrode. The changes that were to be persisted to the item don't apply anymore.
And that's why you lose the changes made by the user.
When you use ItemUpdated instead, the changes made by the user are persisted because they are saved before you do anything. Then you call that Update() inside an ItemUpdated event. That one is either throwing a stack overflow exception silently or doing something else completely crazy, because you've created an infinite recursion loop there - and that's why you don't see it changing the title.
If you want to add extra changes to an item being saved by the UI, modify the AfterProperties property of properties instead of changing them directly in the item.