You can expose an object in an add-in to the following types of Office solutions:

• Other Visual Studio Tools for Office add-ins.

• Document-level customizations that are loaded in the same application process as your add-in.

• COM add-ins (that is, add-ins that implement the IDTExtensibility2 interface directly).

• Visual Basic for Applications (VBA) code in a document that is loaded in the same application process as your add-in.

To expose an object to other add-ins, override the RequestComAddInAutomationService method in the ThisAddIn class. Return the object that you want to expose to other Office solutions.

When your add-in is loaded, the Visual Studio Tools for Office runtime calls the RequestComAddInAutomationService method. The runtime assigns the returned object to the Object property of a COMAddIn object that represents your add-in. This COMAddIn object is available to other Office solutions.

Requirements of the Returned Object

Example

Private utilities As AddInUtilities

Protected Overrides Function RequestComAddInAutomationService() As Object
    If utilities Is Nothing Then
        utilities = New AddInUtilities()
    End If
    Return utilities
End Function

private AddInUtilities utilities;

protected override object RequestComAddInAutomationService()
{
    if (utilities == null)
        utilities = new AddInUtilities();

    return utilities;
}

In the code of a different Office solution (not the exposed add-in), perform the following steps:

1. Get the COMAddIn object that represents the exposed add-in. You can access all of the available add-ins by using the COMAddIns property of the Application class.

2. Access the Object property of the COMAddIn object.

The following code example demonstrates how to use VBA to call a method in an add-in. This VBA macro calls a method named ImportData that is defined in an add-in that is named ExcelImportData. To see this code in the context of a larger walkthrough, see Walkthrough: Calling Code in an Application-Level Add-in from VBA.

Sub CallVSTOMethod()
    Dim addIn As COMAddIn
    Dim automationbject As Object
    Set addIn = Application.COMAddIns("ExcelImportData")
    Set automationObject = addIn.Object
    automationObject.ImportData
End Sub

Concepts