Event Handler Example

Requirement: In a Project collaboration SharePoint site, had a requirement to Allow users to upload only PDF files to a Document library and prevent all other files from being uploaded.

Solution: Our requirement is basically to prevent files being uploaded other than PDF, Isn't it? So lets jump to visual studio and create a Event Receiver in SharePoint to prevent all other file types.

How to Create a Event Receiver in SharePoint 2010?
Compared with MOSS 2007, Creating Event receivers in SharePoint 2010 is very easy With Visual Studio 2010. Here are the steps:

1. Create a New Visual Studio Project, Choose SharePoint >> 2010 >> Event Receiver >> Give it a Name. Say "Crescent.ProjectSites.AllowPDFOnly"

2. Make it as a Farm solution, choose the event receiver properties as in the below screen.

3. On clicking "Finish" button, Visual Studio will create the project structure as:

4. Now, in the Elements.xml file, change the ListTemplateID="101" (Which means all document Libraries) to ListURL="RelativePathOfDocLibrary" say: ProjectDocuments.

Change the <Receivers attribute
5. Update the Event receiver ItemAdding section's code as below:

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if (!properties.AfterUrl.EndsWith("pdf"))             {                 properties.ErrorMessage = "You are allowed to upload only PDF Files!";                 properties.Status = SPEventReceiverStatus.CancelWithError;                 properties.Cancel = true;             }

So, The complete code would be:

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using System; using System.Security.Permissions; using Microsoft.SharePoint; using Microsoft.SharePoint.Security; using Microsoft.SharePoint.Utilities; using Microsoft.SharePoint.Workflow;   namespace Crescent.ProjectSites.AllowPDFOnly.EventReceiver1 {     public class EventReceiver1 : SPItemEventReceiver     {        public override void ItemAdding(SPItemEventProperties properties)        {            base.ItemAdding(properties);              if (!properties.AfterUrl.EndsWith("pdf"))            {                properties.ErrorMessage = "You are allowed to upload only PDF Files!";                properties.Status = SPEventReceiverStatus.CancelWithError;                properties.Cancel = true;            }        }     } }

See the the result in action!

Drawback: This will prevent creating sub-folders which doesn't end with PDF! so if you need folder, name it like "folder.pdf" and then rename!

Read more: http://www.sharepointdiary.com/2012/07/allow-only-certain-file-types-to-be.html#ixzz2HNFx6MvQ