Useful SharePoint Designer Activities and SharePoint Designer 2010

It did not come as a surprise that Microsoft has added functionality into SPD 2010 that some of the activities created as a part of my open source project on CodePlex accomplished. At this year’s SharePoint Conference in Las Vegas I made it a point to go and check out some of the SPD 2010 sessions. I was pleasantly surprised by the new functionality that was added to SPD and you got to love the ribbon interface. On a sad note the most popular set of activities on the CodePlex project, the Permission Activities, are now available out of the box. There was a moment during one of the SPD 2010 demos when the guy said “and now we are going to set permissions on this item” I thought to myself “Oh, well, I’m just going to have to find another niche for the open source project”. From what I saw not all of the functionality provided by my project is in SPD 2010. For instance, “Start another workflow” is not part of the new functionality. Once I get my hands on a stable Beta of WSS and SPD 2010 I will create a roadmap for the still needed custom activities that may be implemented in the next version of the Useful SharePoint Designer Activities Project. Stay Tuned.

SharePoint List Query performance gotcha

As i recently discovered, there is BIG difference between calling SPList.GetItemById() and SPList.Items.GetItemById(). The latter causes all items to be loaded into memory and then filtered. This can cause severe performance issues for lists with large number of items.
Below is the code that takes 5 hours to run on a dual core box when run against a list with 5500 items.

   1:  SPList theList = GetList(); 

   2:   

   3:  List<int> itemIds = new List<int>();  

   4:   

   5:  foreach(SPListItem item in theList.Items)   

   6:  {  

   7:   itemIds.Add(item.ID);

   8:  } 

   9:   

  10:  foreach(int itemId in itemIds)  

  11:  { 

  12:   

  13:    SPListItem theItem =  theList.Items.GetItemById(itemId); //this will cause severe performance issues for large lists

  14:   

  15:  }

To fix this issue we need to change the code in line 13 to:

  13:  SPListItem theItem =  theList.GetItemById(itemId);

Now the above code will run in minutes.

I wish MSDN documentation on this topic was more clear. That would save me from putting in a couple of late nights at the office.

Disable event firing in SharePoint when updating a list item outside of an event handler

As you probably know, when developing Event Handlers for SharePoint you have the option turning off event firing. This functionality is exposed through SPEventReceiverBase.DisableEventFiring() Method . This is very useful when you are updating the item from within the event handler and do not want an infinite loop to occur.

During my last project i discovered that you cannot disable event firing from code that is not part of an event handler, because DisableEventFiring() is an internal instance method. Still, i was determined to find a solution. So i whipped out Reflector and started investigating. Upon disassembling Microsoft.Sharepoint.dll, I discovered that the above mentioned method actually sets a static, thread-specific, property of SPEventManager class called EventFiringDisabled. SPEventManager class is responsible for instantiating event handlers and delivering events to them. Because this class is marked "internal", it is not intended for use by SharePoint API consumers . But what is a good solution without some HACKS? :) I used reflection to set EventFiringDisabled property.

Below, you will find my solution neatly wrapped in a class. Please use at your own risk.

using System;

using System.Collections.Generic;

using System.Text;

using System.Reflection;

using Microsoft.SharePoint;


/// provides access to the internal Microsoft.SharePoint.SPEventManager class by using reflection

/// sample usage:

/// SPEventManagerWrapper.DisableEventFiring();

/// SPList myList = SPContext.Current.Web.Lists["Shared Documents"];

/// myList.Items[0].Update();

/// SPEventManagerWrapper.EnableEventFiring();

public static class SPEventManagerWrapper

{

private static readonly string _className = "Microsoft.SharePoint.SPEventManager";

private static readonly string _eventFiringSwitchName = "EventFiringDisabled";

private static Type _eventManagerType;




/// gets the status of event firing on the current thread

public static bool EventFiringDisabled

{

get { return GetEventFiringSwitchValue(); }

}


private static Type EventManagerType

{

get

{



if (_eventManagerType == null)

GetEventManagerType();



return _eventManagerType;



}

}



/// enables event firing on the current thread

public static void EnableEventFiring()

{

SetEventFiringSwitch(false);



}



/// disables sharepoint event firing on the current thread

public static void DisableEventFiring()

{

SetEventFiringSwitch(true);



}





/// sets the event firing switch on Microsoft.SharePoint.SPEventManager class using reflection

private static void SetEventFiringSwitch(bool value)

{

PropertyInfo pi = EventManagerType.GetProperty(_eventFiringSwitchName, System.Reflection.BindingFlags.Static System.Reflection.BindingFlags.NonPublic);



pi.SetValue(null, value, null);



}



private static bool GetEventFiringSwitchValue()

{

PropertyInfo pi = EventManagerType.GetProperty(_eventFiringSwitchName, System.Reflection.BindingFlags.Static System.Reflection.BindingFlags.NonPublic);



object val = pi.GetValue(null, null);



return (bool)val;



}



private static Type GetEventManagerType()

{

_eventManagerType = typeof(SPList).Assembly.GetType(_className, true);



return _eventManagerType;

}

}