How to Create an Event Handler to Force Unique in SharePoint?
Long back, I did an Event handler to prevent duplicates in a SharePoint list. There is a another requirement of same kind now. This time, Let me do it with WSP builder. Requirement is simple – Prevent duplicate titles from a List. Hmm.., But in SharePoint 2010 this is an instinct feature, we don’t need to do any event handlers.
Lets get started.
Create an Event handler for SharePoint 2007 with WSP Builder – Step by step:
Step 1: Open the Visual studio, Create a New Project, Choose WSP Builder Project type
Step 2: Add a new item to the Project
Step 3: Choose Event Handler under WSP Builder node, Name it and click “Add”
Step 4: In the Event Handler code, place this code:
using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.SharePoint;
namespace PreventDuplicateEventHandler
{
class PreventDuplicates : SPItemEventReceiver
{
public override void ItemAdding(SPItemEventProperties properties)
{
base.ItemAdding(properties);
try
{
using(SPSite oSPSite= new SPSite(properties.WebUrl))
{
SPWeb oSPWeb = oSPSite.OpenWeb();
SPList oSPList = oSPWeb.Lists[properties.ListId];
SPQuery oSPquery = new SPQuery();
oSPquery.Query = @"<Where><Eq><FieldRef Name='Title' /><Value Type='Text'>" + properties.AfterProperties["Title"] + "</Value></Eq></Where>";
SPListItemCollection oListItemColl = oSPList.GetItems(oSPquery);
if (oListItemColl.Count > 0)
{
properties.Cancel = true;
properties.ErrorMessage = "There is already an item with the title " + properties.AfterProperties["Title"] + " in this list";
}
}
}
catch (Exception ex)
{
System.Diagnostics.EventLog.WriteEntry("Error encountered in Event Handler", ex.Message);
}
}
}
}
Step 5: Build the project, Build the WSP, Deploy the WSP.
Step 6: Navigate to the site, go to Site settings >> Site features >> and then activate “Prevent Duplicate” feature.
Step 7: Now, we have the feature ready. We have to associate the event handler with our List. To do that, there are a lot of tools available. Here is one of them: Download and run the executable. (By the way, You can write your own code to register the event handler)
Step 8: Register the event handler to the desired list.
Found a bug in the above tool! use the SharePoint Event Receiver Manager instead!!!
That’s all. We are done, See it in action!!
I set properties.Cancel = true and properties.ErrorMessage = “Custom Validation Error Message” in the itemUpdating synchronous event receiver method. Instead of seeing the SharePoint error page, I am getting the IIS server error page with the full stack trace, etc. What am I missing?
Really nice article!!
But remember that SPQuery only works with up to 2000 items limit.
Helpful links:
https://msdn.microsoft.com/en-us/library/bb687949(v=office.12).aspx#UsingSPQueryObjs
https://blogs.msdn.com/b/sowmyancs/archive/2008/10/26/best-practices-sharepoint-object-model-for-performance-tuning.aspx
Thanks!
Thanks for the walthrough. Could you please fix the link given in step# 7
Fixed!
Thank you for your real quick response buddy!
thanks fo helping me out