Accessing SharePoint lookup fields values in item receivers - some pitfalls.


Recently I was playing with synchronous item event receivers and lookup fields and found some interesting behavior in different situations. I'll try to describe some pitfalls that I faced when develop item receivers for SharePoint.

So, lookup fields. When you try access to a lookup field in such events as Adding or Updating you may to have lookup value. But AfterProperties always contain only lookup Id, if you want to get lookup value you must query item by id. Imagine you have a list named "Software", it has title field and category lookup field (now we have 19 category types in "Category" list). When we try to add new item in "Software" list in ItemAdding event we can see:

Where "18" is an Id of category. And ItemAdded:

So, when use class SPFieldLookupValue, in ItemAdding event LookupValue equal to null (in AfterProperties) and not null in ItemAdded(in ListItem).

Let's try to update this item:

Situation is very similar - in AfterProperties we have an item Id (LookupId in SPFieldLookupValue class, LookupValue is null), and value in ListItem. In ItemUpdated event as you may know we will have both lookupId and LookupValue. Be aware of this SharePoint behavior.


How to upgrade feature in SharePoint 2010 using Visual Studio


Please, refer to my revisited post, it contains more solid and working example of upgrading features using visual studio.

Today I'm going to explain how to use new SharePoint 2010 enhancement - feature upgrade. I'll create small example just to show how it works. First of all let's create new Visual Studio project and add new feature named "SomeFeature". Our feature will be install new list instance to site - Tasks list. In feature settings specify version of your feature, it must be set to "". Deploy you project and make sure that your feature successfully install and new list appear. Its time to upgrade now. There is no command "Upgrade" in Visual Studio, that why we'll create own command using nice CKSDEV plugin. Go to the project settings and create new deployment configuration "UpagradeFeatures". There are three steps in configuration - Recycle IIS Application pool and two steps named "Run PowerShellScrips" from CKSDEV extension.

First script will be update our solution (.wsp file) in configuration database, the second one will find all features that need to be upgraded and call method "Upgrade" on each. Upgrade will be fire only on those features, that have version number is less than appropriate number in configuration database. SPWebApplication class has a method QueryFeatures that returns all features in web application that need to be upgraded.
Here is a code in file UpdateSolution.ps1:

param([string]$solutionPackageName, [string]$solutionPackagePath)
Add-PSSnapin Microsoft.SharePoint.Powershell -EA SilentlyContinue

$solution = Get-SPSolution | where-object {$_.Name -eq $solutionPackageName}
if ($solution -ne $null) {
  if($solution.Deployed -eq $true){
    Write-Host "Updating old version of solution package"
    Update-SPSolution -Identity $solutionPackageName -LiteralPath $solutionPackagePath -Local -GACDeployment
    Write-Host "Solution has been updated"
  else {
    Write-Host "Solution package cannot be updated because it is not currently deployed"  


How to extend deployment of sharepoint solution in Visual Studio using "Run PowerShell script" deployment step.

Hi2all! Today I'm going to explain how you can easily extend your deployment tasks using Visual Studio and plugin CKSDEV for Visual Studio 2010. This plugin enhance VS with many custom SharePoint project items (SPI), add additional deployment configuration for your project and some other useful details. One of the most great possibilities that CKSDEV offer are additional deployment steps:

Imagine that after deployment you must create on the site several sharepoint groups and assign permission to them. Using deployment step "Run PowerShell Script" you can place all logic reside to group creation to your custom powershell script file and execute this script file after deployment. We start with creation of script file and then we integrate script in Visual Studio 2010.
I've been created xml file definition for groups that have such structure:


Now lets create two files - in the first we are storing all functions and the second will use functions from this file. Call the first file "functions.ps1" and the second - "starter.ps1". "functions.ps1" include function "AddGroups" that actually read xml with group definition and adds required groups to a site. I will explain in other post how my code work, but it rather simple, if you have base knowledges of powershell you easily understand it:


Changing default view for ListViewWebPart programmatically.

Hi2all! Recently I faced with problem of changing default view for ListViewWebPart. My ListViewWebPart placed is on the meeting workspace site, on default.aspx page.I need to switch view programmatically to custom. Ok, at first glance not so hard. We must take instance of our webpart and set it property “ViewGuid” equal to custom view id in list, which is associated with webpart. Here is a peace of code:

var file = workspaceWeb.Files["default.aspx"];
var wpMngr = file.GetLimitedWebPartManager(PersonalizationScope.Shared);
var attendeeListViewWebPart = (ListViewWebPart)wpMngr.WebParts.Cast<WebPart>().FirstOrDefault(w => w.Title.Equals("Attendees"));
var list = workspaceWeb.Lists["Attendees"];
var view = list.Views["Attendees"];
attendeeListViewWebPart.ViewGuid = view.ID.ToString("B").ToUpper();

But it not works as expected. I get reference to SPLimitedWebPartManager, find my webpart and try to update ViewGuid, but every time I try to save changes I get error “The specified view is invalid”. Very strange behavior I suppose. I try to solve this issue about 8 hours and I find solution at last. May be it will be surprise for you, but every time when you add ListViewWebPart to a page, it internally creates hidden view in list. This hidden view belong to this webpart, it id generates by webpart and webpart set its own ViewGuid equal to this id. Let’s check it using SharePoint Manager 2010. I create test site collection from blank site and create links list named “dummy”. Let’s go to SharePoint Manager: