Customizing UI Features By Using Extensibility Interfaces

The Office development tools in Visual Studio provide classes and designers that handle many implementation details when you use them to create custom task panes, ribbon customizations, and Outlook form regions in an application-level add-in. However, you can also implement the extensibility interface for each feature yourself if you have special requirements.

Applies to: The information in this topic applies to application-level projects for Microsoft Office 2013 and Microsoft Office 2010. For more information, see Features Available by Office Application and Project Type.

Overview of Extensibility Interfaces

Microsoft Office defines a set of extensibility interfaces that COM add-ins can implement to customize certain features, such as the ribbon. These interfaces provide full control over the features they provide access to. However, implementing these interfaces requires some knowledge of COM interoperability in managed code. In some cases, the programming model of these interfaces is also not intuitive for developers who are accustomed to the .NET Framework.

When you create an add-in by using the Office project templates in Visual Studio, you do not have to implement the extensibility interfaces to customize features like the ribbon. The Visual Studio Tools for Office runtime implements these interfaces for you. Instead, you can use more intuitive classes and designers provided by Visual Studio. However, you can still implement the extensibility interfaces directly in your add-in if you want to.

For more information about the classes and designers that Visual Studio provides for these features, see Custom Task Panes, Ribbon Designer, and Creating Outlook Form Regions.

Extensibility Interfaces You Can Implement in an Add-In

The following table lists the extensibility interfaces you can implement and the applications that support them.





Implement this interface to customize the ribbon UI.

> [!NOTE] >

You can add a Ribbon (XML) item to a project to generate a default Microsoft.Office.Core.IRibbonExtensibility implementation in your add-in. For more information, see Ribbon XML.

Excel 2013

InfoPath 2013

Outlook 2013

PowerPoint 2013

Project 2013

Visio 2013

Word 2013

Excel 2010

InfoPath 2010

Outlook 2010

PowerPoint 2010

Project 2010

Visio 2010

Word 2010


Implement this interface to create a custom task pane.

Excel 2013

Outlook 2013

PowerPoint 2013

Word 2013

Excel 2010

Outlook 2010

PowerPoint 2010

Word 2010


Implement this interface to create an Outlook form region.

Outlook 2013

Outlook 2010

There are several other extensibility interfaces that are defined by Microsoft Office, such as Microsoft.Office.Core.IBlogExtensibility, Microsoft.Office.Core.EncryptionProvider, and Microsoft.Office.Core.SignatureProvider. Visual Studio does not support implementing these interfaces in an add-in created by using the Office project templates.

Using Extensibility Interfaces

To customize a UI feature by using an extensibility interface, implement the appropriate interface in your add-in project. Then, override the RequestService method to return an instance of the class that implements the interface.

For a sample application that demonstrates how to implement the Microsoft.Office.Core.IRibbonExtensibility, Microsoft.Office.Core.ICustomTaskPaneConsumer, and Microsoft.Office.Interop.Outlook.FormRegionStartup interfaces in an add-in for Outlook, see the UI Manager Sample in Office Development Samples.

Example of Implementing an Extensibility Interface

The following code example demonstrates a simple implementation of the Microsoft.Office.Core.ICustomTaskPaneConsumer interface to create a custom task pane. This example defines two classes:

  • The TaskPaneHelper class implements Microsoft.Office.Core.ICustomTaskPaneConsumer to create and display a custom task pane.

  • The TaskPaneUI class provides the UI of the task pane. The attributes for the TaskPaneUI class make the class visible to COM, which enables Microsoft Office applications to discover the class. In this example, the UI is an empty UserControl, but you can add controls by modifying the code.


    To expose the TaskPaneUI class to COM, you must also set the Register for COM Interop property for the project. For more information, see Managing Compilation Properties.

Public Class TaskPaneHelper
    Implements Office.ICustomTaskPaneConsumer

    Friend taskPane As Office.CustomTaskPane

    Public Sub CTPFactoryAvailable(ByVal CTPFactoryInst As Office.ICTPFactory) _
        Implements Office.ICustomTaskPaneConsumer.CTPFactoryAvailable

        If CTPFactoryInst IsNot Nothing Then 
            ' Create a new task pane.
            taskPane = CTPFactoryInst.CreateCTP( _
                "Microsoft.Samples.Vsto.VB.TaskPaneUI", "Contoso")
            taskPane.Visible = True 
        End If 
    End Sub 
End Class

<System.Runtime.InteropServices.ComVisible(True)> _
<System.Runtime.InteropServices.ProgId("Microsoft.Samples.Vsto.VB.TaskPaneUI")> _
<System.Runtime.InteropServices.Guid("FFA0920E-F7A5-453d-8AB2-249F4C25B4B2")> _
Public Class TaskPaneUI
    Inherits UserControl
End Class
public class TaskPaneHelper : Office.ICustomTaskPaneConsumer
    internal Office.CustomTaskPane taskPane;

    public void CTPFactoryAvailable(Office.ICTPFactory CTPFactoryInst)
        if (CTPFactoryInst != null)
            // Create a new task pane.
            taskPane = CTPFactoryInst.CreateCTP(
            taskPane.Visible = true;

public class TaskPaneUI : UserControl

For more information about implementing Microsoft.Office.Core.ICustomTaskPaneConsumer, see Creating Custom Task Panes in the 2007 Office System in the Microsoft Office documentation.

Example of Overriding the RequestService Method

The following code example demonstrates how to override the RequestService method to return an instance of the TaskPaneHelper class from the previous code example. It checks the value of the serviceGuid parameter to determine which interface is being requested, and then returns an object that implements that interface.

Friend taskPaneHelper1 As TaskPaneHelper

Protected Overrides Function RequestService( _
    ByVal serviceGuid As Guid) As Object 

    If (serviceGuid = GetType(Office.ICustomTaskPaneConsumer).GUID) Then 
        If (taskPaneHelper1 Is Nothing) Then
            taskPaneHelper1 = New TaskPaneHelper()
        End If 
        Return taskPaneHelper1
    End If 

    Return MyBase.RequestService(serviceGuid)
End Function
internal TaskPaneHelper taskPaneHelper1;

protected override object RequestService(Guid serviceGuid)
    if (serviceGuid == typeof(Office.ICustomTaskPaneConsumer).GUID)
        if (taskPaneHelper1 == null)
            taskPaneHelper1 = new TaskPaneHelper();
        return taskPaneHelper1;

    return base.RequestService(serviceGuid);

See Also


How to: Create Office Projects in Visual Studio


Calling Code in Application-Level Add-ins from Other Office Solutions

Architecture of Application-Level Add-Ins

Other Resources

Office Development Samples and Walkthroughs

Programming Application-Level Add-Ins

Developing Office Solutions