Implementing Event Handler in Sharepoint

Chandresh Pansuriya
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Here I am sharing with you all, how to implement Event Handler Feature in sharepoint and how to activate it.

Below example shows how to add a simple event handler that prevents items from being deleted from a list. Two procedures are involved in this task:

Creating an event handler in Microsoft Visual Studio
Adding the event handler as a Feature in SharePoint

To create the event handler in Visual Studio

Create a new project in Visual Studio by clicking File, pointing to New, and then clicking Project.
In the New Project dialog box, select Visual C# in the Project types box, select Class Library in the Templates box, type DeletingEventHandler in the Name box, and then click OK.
In Solution Explorer, select DeletingEventHandler, and click Add Reference on the Project menu.
In the Add Reference dialog box, select Microsoft.SharePoint on the .NET tab and then click OK.
In the Code Editor, import the Microsoft.SharePoint namespace as follows.

Change the name of the class like DeleteItemEvent and Inherit it from the SPItemEventReceiver class, as follows.

public class DeleteItemEvent : SPItemEventReceiver

Now add code within the class to override the ItemDeleting method given Belowe.

public class DeleteItemEvent : SPItemEventReceiver
{
    public override void ItemDeleting(SPItemEventProperties properties)
    {
        properties.Cancel = true;
        properties.ErrorMessage = "Deleting item from" + " " + properties.ListTitle + " " + "is not supported";
    }
}

Now go to Project menu in visual studio, in this last option is DeleteItemEvent Properties click the Signing tab, select Sign the assembly, select Choose a strong name key file, and then click <New...>.

In the Create Strong Name Key dialog box, type DeletingEventHandler.snk in the Key file name box, optionally specify a password for the key, and then click OK.

To build the project, click Build Solution on the Build menu, or press CTRL+SHIFT+B.

Find the \DeletingEventHandler\bin\Debug folder in the Visual Studio Projects folder, and drag the DeletingEventHandler.dll file to Local_Drive:\WINDOWS\assembly to place the DLL in the global assembly cache.

To add the event handler as a Windows SharePoint Services Feature

Create a folder in Local_Drive:/Program Files/Common Files/Microsoft Shared/web server extensions/12/TEMPLATE/FEATURES called DeletingEventHandler.
Create a Feature.Xml file in this folder like the following that identifies the Feature and its element manifest file and sets the Feature scope to Web site.

Here generate a GUID by running guidgen.exe located in Local_Drive:\Program Files\Microsoft Visual Studio 8.

The Elements.xml file is given below. It is referenced in Feature.xml file in ElementManifest Location tag.

<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
<Receivers ListTemplateId="101">
    <Receiver>
    <Name>DeletingEventHandler</Name>
    <Type>ItemDeleting</Type>
    <SequenceNumber>22500</SequenceNumber>
    <Assembly>ItemAddedEvent, Version=1.0.0.0, Culture=neutral,
    PublicKeyToken=d6009c72158cb154</Assembly>
    <Class>ItemAddedEvent.ItemAddedEvent</Class>
    <Data></Data>
    <Filter></Filter>
    </Receiver>
</Receivers>
</Elements>

Here in Name tag you have to give DLL name. In assembly change info of same for that. Find DLL in GAC and right click on DLL and click on property in that give all the information related to assembly.

In Class tag you have to give Namespace.classname.

In the first tag Receivers "ListtemplatedId" means on which list you have to perfom the Event Handler like Document Library, Custom List, PictureLibrary...etc. Here 101 means Document Library. List of ListTemplated Id are given below.

100 Generic list
101 Document library
102 Survey
103 Links list
104 Announcements list
105 Contacts list
106 Events list
107 Tasks list
108 Discussion board
109 Picture library
110 Data sources
111 Site template gallery
112 User Information list
113 Web Part gallery
114 List template gallery
115 XML Form library
116 Master pages gallery
117 No-Code Workflows
118 Custom Workflow Process
119 Wiki Page library
120 Custom grid for a list
130 Data Connection library
140 Workflow History
150 Gantt Tasks list
200 Meeting Series list
201 Meeting Agenda list
202 Meeting Attendees list
204 Meeting Decisions list
207 Meeting Objectives list
210 Meeting text box
211 Meeting Things To Bring list
212 Meeting Workspace Pages list
301 Blog Posts list
302 Blog Comments list
303 Blog Categories list
1100 Issue tracking
1200 Administrator tasks list

In command prompt, navigate to \Program Files\Common Files\Microsoft Shared\web server extensions\12\BIN on the local drive, and type each of the following commands to install the Feature in the deployment, activate the Feature on a specified subsite, and reset Microsoft Internet Information Services (IIS) so that the changes take effect:

stsadm -o installfeature -filename DeletingEventHandler\Feature.xml
stsadm -o activatefeature -filename DeletingEventHandler\Feature.xml -url http://Server/Site/Subsite
iisreset

Try to delete a Document in Document Library on the specified Web site to see the effect of the event handler feature. Output will look like this.