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Coding Event Receivers with Visual Studio Extensions for Windows Sharepoint Services (VSeWSS) is easy; you add it into your project using Add New Item –> Sharepoint / Event Receiver. You dont need to add “EventReceiver” in the name; as it will automatically post fix; ItemEventReceiver and ListEventReceiver names to the two classes that it generates. It also generates two associated XML files for events which VSeWSS uses and when deploying/packaging the VSeWSS generates two feature.xml files under PKG folder. Simply uncomment the event you need in the generated CS files and write your code into it. And instance of SPItemEventProperties is passed to each event.

• Dont forget to call this.DisableEventFiring() before updating any list item; and this.EnableEventFiring() before exiting. Use try/finally for this!
• You can use the display names of the field when using properties.ListItem, but you need to use the (Internal)Name of the field with properties.AfterProperties and properties.BeforeProperties
• Usually the internal name of fields having spaces is different; the spaces are replaced with _x0020_
• properties.ListItem always contain the current data of the list item for which event has been received; the BeforeProperties get populated for “ed” events; (Added, Updated, Deleted etc) and AfterProperties get populated for “ing” events; (Adding, Updating, Deleting etc)
• There is some bug in Sharepoint List Eventing due to which properties.AfterProperties.ChangedProperties and/or properties.BeforeProperties.ChangedProperties doesnt give correct values; I didnt checked it myself; I just read it somewhere!

Deploying to plain Windows Sharepoint Services (WSS) works fine; but if you deploy your work to Sharepoint Portal Server (SPS); it doesnt; thats because in the ItemEventReceiver.xml file; the VSeWSS makes only the class entry and write the Guid of your class. For SPS; you need to enter not only assembly name but also the class name in .NET way. A sample entry is given below. Issue is whenever you create WSP file from VSeWSS; it will always append the entries of its format; so to have your WSP ready for SPS; you will need to edit the WSP file manually. The WSP file is basically a CAB file and you can use third party CAB tool to extract / replace the files in it.

<?xml version="1.0" encoding="utf-8"?>
<Elements Id="bd6deaa8-bb29-4c8f-8441-73ff0ea23007" xmlns="http://schemas.microsoft.com/sharepoint/">
  <Receivers ListTemplateOwner="fbcf9ee9-6883-4443-8049-3d7c15de2dee">
    <Receiver>
      <Name>ItemAdded</Name>
      <Type>ItemAdded</Type>
      <SequenceNumber>1</SequenceNumber>
      <Class>MySharepointArtifacts.ExpenseQueueItemEventReceiver</Class>
      <Assembly>MySharepointArtifacts, Version=1.0.0.0, Culture=neutral, PublicKeyToken=81c24f946f8d399f</Assembly>
    </Receiver>
  </Receivers>
</Elements>

Tips

1. The wizard picks the lists in the VSeWSS project; if you havnt imported your list into VSeWSS using the solution generator (the tip I gave in my earlier post); its the good time to do it before adding your event receiver. 
2. You can move the ItemEventReceiver.xml/cs and ListEventReceiver.xml/cs files to the folder hosting schema.xml and *.aspx files of your list; its good to have coupled things together under single folder
3. You can remove the ItemEventReceiver.xml and ListEventReceiver.xml files all together; and instead of using VSeWSS for creating a feature for your Event Receiver; can use third party app to register your event receivers later once your assembly is on server.
• u2u’ Event Handler Explorer is highly recommended; its WinForms app with source; you can even extract the event registering code from it and write it into some ASPX file if you already have FixMyList.aspx file for fixing Lookup fields; the tip I gave in my earlier post!

Sorry for not posting regularly lately; I was away busy learning/using/preaching and coaching about Silverlight and Sharepoint. All in all, it was great learning expereince!

Sharepoint development is bit tricky to start with. Sharepoint is flexible and thus bit complicated to deal with. There are number of ways for Sharepoint Development. I opted to use Visual Studio Extensions for Windows Sharepoint Services (VseWss) whose latest version is v1.3 March 2009 CTP (Note its CTP; and has some issues) for Visual Studio 2008. They didn't finalized it; instead Visual Studio 2010 Beta 2 came recently which has these extensions built into it.

VseWss only works where Sharepoint itself is running; therefore you need Windows 2003 (atleast) as your OS (which by the way I already use and prefer over XP and Vista as development OS; I RDP to my desktop machine running Win2k3 from my notebook which runs Windows 7). The first tip is that install Windows Sharepoint Services with the login you used on the Windows 2003; choosing Basic mode; that also installs “Windows Internal Database” which is a variant of SQL Server 2005 Express Edition but without any limits of SQLEE. By doing this; not only that all the things gets configured; but also your login will automatically become Sharepoint Administrator and Site Collection Owner of the site it creates. And when you will install VseWss; you will be able to use it without any issues; otherwise setting up deployment with VseWss is bit tricky! Also dont forget to give correct url in the project’ debug setting; VseWss uses it to discover the Sharepoint site!

Sharepoint/VseWss combination gets broken often in early days; and uninstalling these both and reinstalling is the most easiest way to get back to the working state; and for this you might need to uninstall the Windows Internal Database as well; on 32bit OS the command is given below; after the command dont forget to delete the %windir%\sysmsi\ssee folder so that the Config/Content and Search databases gets deleted and on reinstalation you dont get any dormant thing back!

msiexec /x {CEB5780F-1A70-44A9-850F-DE6C4F6AA8FB} callerid=ocsetup.exe

Accessing Windows Internal Database instance using SQL Management Studio is also bit tricky; specify the following as database server with Windows Authentication and you will get connected!

\\.\pipe\mssql$microsoft##ssee\sql\query

Next for debugging you need to specify the following setting in your sharepoint site’ web.config

<compilation batch="false" debug="true">

You also need to consider that last Released version of Sharepoint Services; is pre .NET 3/3.5; so before using any Ajax / Ajax Toolkit or Silverlight 2’ Server Control; you need to first setup the sharepoint web site and the most easiest way is that you open the site folder using Visual Studio’ Add Existing Web Site…Visual Studio 2008 prompts to convert it!

Sharepoint works seamless if you deploy the things into Global Assembly Cache (GAC); simply drag/drop the assembly into %windir%\Assembly; so if you are using Silverlight 2’ Server Control; deploy that assembly into GAC and register it as SafeControl into sharepoint site’ web.config. If you have some other version of assembly; discover its version and public key token by opening %windir%\Assembly and right click > Properties of the assembly.

<SafeControl Assembly="System.Web.Silverlight, Version=2.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" Namespace="System.Web.UI.SilverlightControls" TypeName="*" Safe="True" AllowRemoteDesigner="True" />

WSP Window is Visual Studio Addin that comes with VseWss and through this; you can view WSP content; the output of the VseWss project is basically a WSP and behind the scene PKG folder gets created having feature XML files. If you are using Source Control; dont forget to add this folder into source control. If you are using Team Foundation Server; simplest way is to include PKG folder into the project. Dont forget to enable View All Files and adding any new folder that gets created whenever you add some new sharepoint feature into your VseWss project.

I will strongly recommend to watch BB13 video (Creating SharePoint Applications with Visual Studio 2008) from PDC 2008; and you will realize where/how VseWss can help you. Channel 9 also has few more screencasts on VseWss which are worth seeing.

• http://channel9.msdn.com/posts/pdc2008/tags/Sharepoint; few more sessions on Sharepoint from PDC 2008

From these videos you will learn how you can deploy custom resources (images, HTML files and even ASPX files) into /_layout/; I will suggest to add “12” folder as Toolbar into your Taskbar for easier access to 12 Folder Hive! If you are planning to deploy ASPX files; you can add the ASPX file by adding HTML Page into the VseWss project and renaming it to ASPX. Second, as said earlier; Sharepoint works seamless if you deploy the things into GAC; so when creating the VseWss project; choose Full Trust (Deploy to GAC) option and thirdly  in the ASPX file you might need to give few more details about your assembly; else you will experience Assembly Not Found errors! You can discover the public key token of your assembly the same way like I said about System.Web.Silverlight above!

<%@ Page Language="C#" AutoEventWireup="true" Inherits="MySharepointArtifacts.MyPage, MySharepointArtifacts, Version=1.0.0.0, Culture=neutral, PublicKeyToken=81c24f946f8d399f" %>

There are lot of goodies in .NET 4 for Parallel Programming. There is even a separate dedicated section on it. The following picture from that section explains the four categories of improvement in Framework just for this.

I mentioned earlier that previously I used Abortable Threadpool to implement cancelling work under specific condition. With ThreadPool we never had an easy way to queue the batch of work, know when that batch is completed and do exception handling properly. Things have significantly improved with Task Parallel Library; which is integrated with ThreadPool and resolves all the issues I mentioned plus lot more. Here is small app that does cancelling the tasks after certain time out and investigates the exception if any thrown by the task!

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading;

using System.Threading.Tasks;

namespace TplConsoleApplication

{

    class Program

    {

        static Random random = new Random();

        static void LongWork(int deviceIdentifier, CancellationToken ct)

        {

            Thread.Sleep(2000);

            int r = random.Next(5);

            //Simulating that certain device fails

            if (r > 3)

                throw new ApplicationException(string.Format("{0} failed (by random)", deviceIdentifier));

            Thread.Sleep(r * 2000);

        }

        static void Main(string[] args)

        {

            var tokenSource = new CancellationTokenSource();

            var token = tokenSource.Token;

            List<Task> listOfTasks = new List<Task>();

            for (int i = 0; i < 10; i++)

            {

                int j = i;  //The anonymous delegate will use the latest value by design

                            //If we use the for variable value it will always be the last one

                listOfTasks.Add(Task.Factory.StartNew(() => LongWork(j, token), token));

            }

            Task[] tasks = listOfTasks.ToArray();

            int seconds = 3;

            Thread.Sleep(1000);                     //Give the tasks a second to start

            Console.WriteLine("Waiting {0}secs", seconds);

            Thread.Sleep(seconds * 1000);           //We have 10secs to do all the tasks

            tokenSource.Cancel();                   //After that we need to abort uncompleted tasks

                                                    //If we want we can return/exit here; the cancelled tasks will

                                                    //  be taken care

            #region The region is optional; in case we want to know what happened

            try

            {

                Task.WaitAll(tasks);

            }

            catch (AggregateException e)

            {

                foreach (var v in e.InnerExceptions)

                {

                    if (!(v is TaskCanceledException))

                        Console.WriteLine(v.Message);

                }

            }

            for (int i = 0; i < tasks.Length; i++)

                Console.WriteLine("task[{0}] status is now {1}, IsCancelled={2}", i, tasks.Status, tasks.IsCanceled);

            #endregion

            Console.ReadLine();

        }

    }

}

Barrier class is newly introduced in .NET 4 and it enables the multiple tasks to cooperatively work on an algorithm in parallel through multiple phases. For instance you are polling the data from multiple data source; and this polling is multi step process. While polling in parallel you want coordination that on each step the parallel running tasks before moving to next step coordinate with each other. Visual Studio 2010 and .NET Framework 4 Training Kit (October Preview) has a great sample which I am reproducing below!

static Barrier sync;
static CancellationToken token;

static void Main(string[] args)
{
    var source = new CancellationTokenSource();
    token = source.Token;
    sync = new Barrier(3);

    var charlie = new Thread(() => DriveToBoston("Charlie", TimeSpan.FromSeconds(1))); charlie.Start();
    var mac = new Thread(() => DriveToBoston("Mac", TimeSpan.FromSeconds(2))); mac.Start();
    var dennis = new Thread(() => DriveToBoston("Dennis", TimeSpan.FromSeconds(3))); dennis.Start();

    charlie.Join();
    mac.Join();
    dennis.Join();

    Console.ReadKey();
}

static void DriveToBoston(string name, TimeSpan timeToGasStation)
{
    try
    {
        Console.WriteLine("[{0}] Leaving House", name);

        // Perform some work
        Thread.Sleep(timeToGasStation);
        Console.WriteLine("[{0}] Arrived at Gas Station", name);

        // Need to sync here
        sync.SignalAndWait(token);

        // Perform some more work
        Console.WriteLine("[{0}] Leaving for Boston", name);
    }
    catch (OperationCanceledException)
    {
        Console.WriteLine("[{0}] Caravan was cancelled! Going home!", name);
    }
}

The other day I received a query on how to update rows in a table having from clause and self join needs to be used…I thought its interesting scenario and should document it for future references…

Let me explain the problem with a scenario…Lets consider a table in which hierarchy is implemented using Parent / Child to self; something like

create table Employees
(
     EmployeeIndex int,
     ManagerIndex int, --For Parent / Child relationship
     Name nvarchar(50)
);

insert into Employees (employeeindex, managerindex, name) values (1, null, 'Manager');
insert into Employees (employeeindex, managerindex, name) values (2, 1, 'Developer');
insert into Employees (employeeindex, managerindex, name) values (2, 1, 'Tester');

And then lets say we added a column; ProjectIndex pointing to the Projects table key on which these employees working; and lets just update the manager row.

alter table Employees add ProjectIndex int;
update employees set projectindex = 1 where employeeindex = 1;

Now we need to update the Developer and Tester rows…the query will be:

update employees
set projectindex = m.projectindex
from employees join employees m on employees.managerindex = m.employeeindex

Important thing to note is; that we are not aliasing the table in the from clause and that is representing the updating table and its getting joined to the (same) table having alias and that alias is distinguishing it onwards!

If we want to alias the updating table; the update query will become

update members --Note the alias is used which we used in from clause below to represent the updating table
set projectindex = managers.projectindex
from employees members join employees managers on members.managerindex = manager.employeeindex

Sometime while implementing some date/time specific business logic; we need to do some processing on datetime data; e-g trimming away the time, knowing the start of month datetime value. Instead of converting the datetime data to string and then doing some string processing; we can use the SQL Server’ built in functions like dateadd and datediff to do the same…

select
    getdate()                                     [Now],
    datediff(dd, 0, getdate())                    [Difference in days since 0],
    dateadd(dd, datediff(dd, 0, getdate()), 0)    [Start of Today]

select
    getdate()                                     [Now],
    dateadd(mm, datediff(mm, 0, getdate()), 0)    [First day of current month],
    dateadd(wk, datediff(wk, 0, getdate()), 0)    [First day of current week],
    dateadd(hh, datediff(hh, 0, getdate()), 0)    [Start of current hour]

For more details, please read Examples of how to Calculate Different SQL Server Dates article on Database Journal

I started using IE again after IE7 mainly because of its speed and the fact that it has copied all the nice features (Tabs) of Firefox <smile />

IE8 has got some nice developers features (JavaScript debugger with Breakpoints, Native Json support, CSS3 selector to name few) and this video from MSDN Channel 9 is must watch to learn about them; a presentation full of demos by Giorgio Sardo at Microsoft Unplugged!

If you are lucky and using ASP.NET; dont forget to check out Web Application Toolkit at MSDN Code Gallery featuring ASP.NET controls for IE8!!