Extend SharePoint project items
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
Create a project item extension when you want to add functionality to a type of SharePoint project item that is already installed in Visual Studio. For example, you can create an extension for the built-in Event Receiver or List Definition project items in Visual Studio, or you can create an extension for a custom project item type. You can also create an extension for all types of SharePoint project items.
Tasks for extending SharePoint project items
To extend a project item, build a Visual Studio extension assembly that implements the ISharePointProjectItemTypeExtension interface. For more information, see How to: Create a SharePoint project item extension.
When you extend a project item, you can also add the following functionality to the project item:
Add a shortcut menu item to the project item. The menu item appears when you open the shortcut menu for the project item in Solution Explorer. You open the shortcut menu by right-clicking the project item or by choosing it and then choosing the Shift+F10 keys. For more information, see How to: Add a shortcut menu item to a SharePoint project item extension.
Add a custom property to the project item. The property appears in the Properties window when you choose the project item in Solution Explorer. For more information, see How to: Add a property to a SharePoint project item extension.
For a walkthrough that demonstrates how to create, deploy, and test a project item extension, see Walkthrough: Extend a SharePoint project item type.
Understand the relationship between project item extensions and project item instances
When you create a project item extension, Visual Studio loads your extension when a project item of the associated type is added to a SharePoint project. For example, if you create an extension for Event Receiver project items, Visual Studio loads your extension when a user adds an Event Receiver project item to a project. Visual Studio uses the same instance of your extension for all instances of the associated project item type. In the previous example, if the user adds a second Event Receiver project item to the project, the same instance of your extension is used to customize the second project item.
To access a specific instance of the project item type you are extending, handle one of the ISharePointProjectItemEvents events of the projectItemType parameter in your implementation of the Initialize method. For example, to determine when a project item of the type you are extending is added to a project, handle the ProjectItemAdded event. For more information, see How to: Create a SharePoint project item extension.
Identifiers for SharePoint project items
Each SharePoint project item has a corresponding string identifier. You must know the identifier for a project item if you want to perform the following tasks:
Create an extension for the project item. In this case, you must pass the identifier for the project item that you want to extend to the constructor of the SharePointProjectItemTypeAttribute. To create an extension for all project item types, pass the \* string value.
Add the project item to a project programmatically. In this case, you must pass the identifier for the project item to the Add method.
The following table lists the identifiers for the SharePoint project items that are included with Visual Studio.
| Project item name | String identifier |
|---|---|
| Business Data Catalog Model | Microsoft.VisualStudio.SharePoint.BusinessDataConnectivity |
| Content Type | Microsoft.VisualStudio.SharePoint.ContentType |
| Event Receiver | Microsoft.VisualStudio.SharePoint.EventHandler |
| Empty Element | Microsoft.VisualStudio.SharePoint.GenericElement |
| List Definition List Definition From Content Type |
Microsoft.VisualStudio.SharePoint.ListDefinition |
| List Instance | Microsoft.VisualStudio.SharePoint.ListInstance |
| Module | Microsoft.VisualStudio.SharePoint.Module |
| Sequential Workflow State Machine Workflow |
Microsoft.VisualStudio.SharePoint.Workflow |
| Site Definition | Microsoft.VisualStudio.SharePoint.SiteDefinition |
| Visual Web Part | Microsoft.VisualStudio.SharePoint.VisualWebPart |
| Web Part | Microsoft.VisualStudio.SharePoint.WebPart |
| Workflow Association Form | Microsoft.VisualStudio.SharePoint.WorkflowAssociation |