© 2010 Autodesk
Introduction to Revit 2011 API
External Application
Minimum Code in VB.NET
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<C#>
// Hello World #3 - minimum external application
[Transaction(TransactionMode.Automatic)]
[Regeneration(RegenerationOption.Manual)]
public class HelloWorldApp : IExternalApplication
{
    // OnShutdown() - called when Revit ends. 
    public Result OnShutdown(UIControlledApplication application)
    {
        return Result.Succeeded;
    }
 
    // OnStartup() - called when Revit starts.
    public Result OnStartup(UIControlledApplication application)
    {
        TaskDialog.Show("My Dialog Title", "Hello World from App!");
        return Result.Succeeded;
    }
}
</C#>