Calling Code in Document-Level Customizations from VBA

You can configure a document-level project for Word or Excel so that Visual Basic for Applications (VBA) code in the document can call code in the customization assembly. This is useful in the following scenarios:

• You want to extend existing VBA code in a document by using features in a document-level customization that is associated with the same document.

• You want to make services that you develop in a document-level customization available to end users who can access the services by writing VBA code in the document.

Applies to: The information in this topic applies to document-level projects for the following applications: Excel 2007 and Excel 2010; Word 2007 and Word 2010. For more information, see Features Available by Office Application and Project Type.

The Office development tools in Visual Studio provide a similar feature for application-level add-ins. If you are developing an add-in, you can call code in your add-in from other Microsoft Office solutions. For more information, see Calling Code in Application-Level Add-ins from Other Office Solutions.

Requirements

Before you can enable VBA code to call into the customization assembly, your project must meet the following requirements:

• The document must have one of the following file name extensions:

  • For Word: .docm or .doc

  • For Excel: .xlsm, .xltm, .xls, or .xlt

• The document must already contain a VBA project that has VBA code in it.

• VBA code in the document must be allowed to run without prompting the user to enable macros. You can trust VBA code to run by adding the location of the Office project to the list of trusted locations in the Trust Center settings for Word or Excel.

• The Office project must contain at least one public class that contains one or more public members that you are exposing to VBA.

  You can expose methods, properties, and events to VBA. The class that you expose can be a host item class (such as ThisDocument for Word, or ThisWorkbook and Sheet1 for Excel) or another class that you define in your project. For more information about host items, see Host Items and Host Controls Overview.

Enabling VBA Code to Call into the Customization Assembly

There are two different ways that you can expose members in a customization assembly to VBA code in the document:

• You can expose members of a host item class in a Visual Basic project to VBA. To do this, set the EnableVbaCallers property of the host item to True in the Properties window while the host item (that is, the document, worksheet, or workbook) is open in the designer. Visual Studio automatically performs all of the work required to enable VBA code to call members of the class.

• You can expose members in any public class in a Visual C# project, or members in a non-host item class in a Visual Basic project, to VBA. This option provides you with more freedom to choose which classes you expose to VBA, but it also requires more manual steps.

  To do this, you must perform the following main steps:

  1. Expose the class to COM.

  2. Override the GetAutomationObject method of a host item class in your project to return an instance of the class that you are exposing to VBA.

  3. Set the ReferenceAssemblyFromVbaProject property of any host item class in the project to True. This embeds the customization assembly's type library into the assembly and adds a reference to the type library to the VBA project in the document.

For detailed instructions, see How to: Expose Code to VBA in a Visual Basic Project and How to: Expose Code to VBA in a Visual C# Project.

The EnableVbaCallers and ReferenceAssemblyFromVbaProject properties are available only in the Properties window at design time; they cannot be used at run time. To view the properties, open the designer for a host item in Visual Studio. For more information about the specific tasks that Visual Studio performs when you set these properties, see Tasks Performed by the Host Item Properties.

Using Members in VBA Code to Call into the Customization Assembly

After you configure your project to enable VBA code to call into the customization assembly, Visual Studio adds the following members to the VBA project in the document:

• For all projects, Visual Studio adds a global method named GetManagedClass.

• For Visual Basic projects in which you expose members of a host item class by using the EnableVbaCallers property, Visual Studio also adds a property named CallVSTOAssembly to the ThisDocument, ThisWorkbook, Sheet1, Sheet2, or Sheet3 module in the VBA project.

You can use the CallVSTOAssembly property or GetManagedClass method to access public members of the class that you exposed to VBA code in the project.

Using the CallVSTOAssembly Property in a Visual Basic Project

Use the CallVSTOAssembly property to access public members that you added to the host item class. For example, the following VBA macro calls a method named MyVSTOMethod that is defined in the Sheet1 class in an Excel workbook project.

Sub MyMacro()
    Sheet1.CallVSTOAssembly.MyVSTOMethod()
End Sub

This property is a more convenient way to call into the customization assembly than using the GetManagedClass method directly. CallVSTOAssembly returns an object that represents the host item class that you exposed to VBA. The members and method parameters of the returned object appear in IntelliSense.

The CallVSTOAssembly property has a declaration that is similar to the following code. This code assumes that you have exposed the Sheet1 host item class in an Excel workbook project named ExcelWorkbook1 to VBA.

Property Get CallVSTOAssembly() As ExcelWorkbook1.Sheet1
    Set CallVSTOAssembly = GetManagedClass(Me)
End Property

Using the GetManagedClass Method

To use the global GetManagedClass method, pass in the VBA object that corresponds to the host item class that contains your override of the GetAutomationObject method. Then, use the returned object to access the class that you exposed to VBA.

For example, the following VBA macro calls a method named MyVSTOMethod that is defined in the Sheet1 host item class in an Excel workbook project named ExcelWorkbook1.

Sub CallVSTOMethod
    Dim VSTOSheet1 As ExcelWorkbook1.Sheet1
    Set VSTOSheet1 = GetManagedClass(Sheet1)
    VSTOSheet1.MyVSTOMethod
End Sub

The GetManagedClass method has the following declaration.

GetManagedClass(pdispInteropObject Object) As Object

This method returns an object that represents the class that you exposed to VBA. The members and method parameters of the returned object appear in IntelliSense.

Guidelines for Adding VBA Code to the Document

There are several different copies of the document where you can add VBA code that calls into the document-level customization.

As you develop and test your solution, you can write VBA code in the document that opens while you debug or run your project in Visual Studio (that is, the document in the build output folder). However, any VBA code you add to this document will be overwritten the next time that you build the project, because Visual Studio replaces the document in the build output folder with a copy of the document from the main project folder.

If you want to save the VBA code that you add to the document while debugging or running the solution, copy the VBA code into the document in the project folder. For more information about the build process, see Office Solution Build Process Overview.

When you are ready to deploy your solution, there are three main document locations in which you can add the VBA code.

In the Project Folder on the Development Computer

This location is convenient if you have complete control over both the VBA code in the document and the customization code. Because the document is on the development computer, you can easily modify the VBA code if you change the customization code. VBA code that you add to this copy of the document remains in the document when you build, debug, and publish your solution.

You cannot add the VBA code to the document while it is open in the designer. You must first close the document in the designer, and then open the document directly in Word or Excel.

In the Publish or Installation Folder

In some cases, it might be suitable to add the VBA code to the document in the publish or installation folder. For example, you might choose this option if the VBA code is written and tested by a different developer on a computer that does not have Visual Studio installed.

If users install the solution directly from the publish folder, you must add the VBA code to the document every time you publish the solution. Visual Studio overwrites the document in the publish location when you publish the solution.

If users install the solution from an installation folder that is different from the publish folder, you can avoid adding the VBA code in the document every time you publish the solution. When a publish update is ready to be moved from the publish folder to the installation folder, copy all of the files to the installation folder except for the document.

On the End User Computer

If the end users are VBA developers who are calling into services that you provide in the document-level customization, you can tell them how to call your code by using the CallVSTOAssembly property or the GetManagedClass method in their copies of the document. When you publish updates to the solution, VBA code in the document on the end user computer will not be overwritten, because the document is not modified by publish updates.

Tasks Performed by the Host Item Properties

When you use the EnableVbaCallers and ReferenceAssemblyFromVbaProject properties, Visual Studio performs different sets of tasks.

EnableVbaCallers

When you set the EnableVbaCallers property of a host item to True in a Visual Basic project, Visual Studio performs the following tasks:

1. It adds the ComClassAttribute and ComVisibleAttribute attributes to the host item class.

2. It overrides the GetAutomationObject method of the host item class.

3. It sets the ReferenceAssemblyFromVbaProject property of the host item to True.

When you set the EnableVbaCallers property back to False, Visual Studio performs the following tasks:

1. It removes the ComClassAttribute and ComVisibleAttribute attributes from the ThisDocument class.

2. It removes the GetAutomationObject method from the host item class.

   Note

   Visual Studio does not automatically set the ReferenceAssemblyFromVbaProject property back to False. You can set this property to False manually by using the Properties window.

ReferenceAssemblyFromVbaProject

When the ReferenceAssemblyFromVbaProject property of any host item in a Visual Basic or Visual C# project is set to True, Visual Studio performs the following tasks:

1. It generates a type library for the customization assembly and embeds the type library in the assembly.

2. It adds a reference to the following type libraries in the VBA project in the document:

   • The type library for your customization assembly.

   • The Microsoft Visual Studio Tools for Office Execution Engine 9.0 Type Library. This type library is included in the Visual Studio Tools for Office runtime.

When the ReferenceAssemblyFromVbaProject property is set back to False, Visual Studio performs the following tasks:

1. It removes the type library references from the VBA project in the document.

2. It removes the embedded type library from the assembly.

Troubleshooting

The following table lists some common errors and suggestions for fixing the errors.

See Also

Tasks

How to: Expose Code to VBA in a Visual Basic Project

How to: Expose Code to VBA in a Visual C# Project

Walkthrough: Calling Code from VBA in a Visual Basic Project

Walkthrough: Calling Code from VBA in a Visual C# Project

Concepts

Publishing Office Solutions by Using ClickOnce

Other Resources

Combining VBA and Document-Level Customizations

Programming Document-Level Customizations