How to register .NET components with COM


SummaryExtending the ArcGIS applications with custom .NET components requires that the .NET classes are made available to the component object model (COM) runtime by registering the components in the COM registry. The three ways to perform this task are outlined in this document. In addition, if the component is to be used from a COM development environment, you may also want to export a type library, which is also outlined in this document.

Building the project on a development machine

 
When you want to register an assembly for COM interop on a development machine, the simplest way is to open the project in Visual Studio 2005, ensure the project-level Register for COM Interop property is set to true, then build the project.
 
To check a project's settings, click Project Properties from the Project menu, select the Build (C#) or Compile (VB.NET) page, and select the Register for COM Interop check box.
 

Registering by command, using the Regasm utility

 
Sometimes you may want to register an assembly for COM interop without building the project; for example, when first testing your component or if you do not have access to the assemblies source code.
 
In this case, you can use the assembly registration utility Regasm that ships with the .NET Framework Software Development Kit (SDK) or Visual Studio 2005. Regasm will add entries to the registry, which allows a COM (unmanaged) application to consume .NET classes via COM interop.
 
Machines with either Visual Studio 2005 or the freely available .NET Framework SDK will have this utility installed and other machines may not; therefore. this is not a viable solution for general deployment of your components.
 
Using the Regasm command line utility
To use the Regasm command line utility:
 
The following example shows the command used to register the assembly called EditTools with COM. The full path to the assembly should be given unless the current directory of the command prompt is the directory where the assembly is located:
 
regasm EditTools.dll /codebase
 
The /codebase parameter is an optional parameter that adds information to the registry specifying the path on disk of the assembly. If the component is not to be deployed to the global assembly cache (GAC), then this option will be required for ArcGIS to find your component successfully; if the component is installed to the GAC, the option is not required. Regasm has many other options; for a full list, type regasm /? or refer to Microsoft Developer Network (MSDN).
 
Regasm can also be used to unregister assemblies from COM interop, as shown in the following example:
 
regasm EditTools.dll /unregister 
 

Using an installation program

 
Finally, you can create an installation program, which will deploy your component and add to the installation program an automatic registration step that will register your component for COM interop.
 
You can create installation programs by using either third-party installation software or using a Visual Studio Setup Project. For an example of how to create a setup project for a component using WISE, see How to deploy an application.
 

Type libraries for managed components


A type library (.tlb) can also be exported that contains information describing the types in the assembly. You may want to generate a type library for a component if that component will be used from another development environment, such as within the Visual Basic for Applications (VBA) environment embedded with the ArcGIS applications. If you want to add custom commands and tools using the Customize dialog box within the ArcGIS applications, you need to generate a type library.
 
Visual Studio will generate this .tlb automatically if you have checked the Register for COM Interop setting. If you do not have a .tlb for an existing component, one can be generated by using the Regasm utility and the /tlb option. See the following:
 
regasm EditTools.dll /tlb:EditTools.tlb