1. Create the calling application.

   

2. Add the required API references.

   

3. Add Other references.

4. Enter the code below:

   CopyControls and COM

   using System;
   using System.Windows.Forms;
   
   //Add the namespaces
   using Autodesk.Navisworks.Api;
   using Autodesk.Navisworks.Api.Controls;
   using Autodesk.Navisworks.Api.Resolver;
   
   using ComApi = Autodesk.Navisworks.Api.Interop.ComApi;
   using ComApiBridge = Autodesk.Navisworks.Api.ComApi;
   
   
   namespace ControlsAndCOM
   {
      class Program
      {
         [STAThreadAttribute]
         static void Main(string[] args)
         {
            // The "Navisworks.Autodesk.Resolver" assembly should be included in your installation.
            // Other Navisworks.Autodesk.*" assemblies will be resolved at runtime,
            // and thus should not be included.
            // Autodesk.Navisworks.Controls controls usage inside the VS Designer is deprecated, and instead they should be created dynamically.
            String runtimeName = Resolver.TryBindToRuntime(RuntimeNames.Any);
            if(String.IsNullOrEmpty(runtimeName))
            {
               throw new Exception("Failed to bind to Navisworks runtime");
            }
            XMain();
         } 
   
         static void XMain()
         {
            //Set to single document mode
            Autodesk.Navisworks.Api.Controls.ApplicationControl.ApplicationType = ApplicationType.SingleDocument;
   
            //Initialise the api
            ApplicationControl.Initialize();
   
            //Create a DocumentControl
            DocumentControl documentControl = new DocumentControl();
   
            //Set as main document, needs to be called as COM works on the application's MainDocument
            documentControl.SetAsMainDocument();
   
            //Dialog for selecting the Location of the file to open
            OpenFileDialog dlg = new OpenFileDialog();
   
            //Ask user for file location
            if (dlg.ShowDialog() == DialogResult.OK)
            {
               //If the user has selected a valid location, then tell DocumentControl to open the file
               if (documentControl.Document.TryOpenFile(dlg.FileName))
               {
                  //Select the first root item using the API
                  ModelItemCollection newSelection = new ModelItemCollection();
                  newSelection.Add(documentControl.Document.Models.First.RootItem);
                  documentControl.Document.CurrentSelection.CopyFrom(newSelection);
   
                  //now query the selection using the COM API
                  ComApi.InwOpState10 state;
                  state = ComApiBridge.ComApiBridge.State;
   
                  foreach (ComApi.InwOaPath path in state.CurrentSelection.Paths())
                  {
                     ComApi.InwOaNode node;
                     node = path.Nodes().Last() as ComApi.InwOaNode;
                     MessageBox.Show("UserName=" + node.UserName);
                  }
               }
            }
   
            //Dispose of the DocumentControl
            documentControl.Dispose();
   
            //Finish use of the API.
            ApplicationControl.Terminate();
         }
   
   
      }
   
   
   }

5. Build and run.

Note
SetAsMainDocument must be called when using DocumentControl with the COM API.

The COM API was written without .NET in mind. So it is important to ensure that all related properties are kept from being disposed by the Garbage Collector until the process being worked on is complete. For example, let us look at the following code excerpt.

CopyErroneous code

foreach (InwOaPath path in sel.Paths())
{
   InwGUIPropertyNode2 propertyNode;
   List<InwOaProperty> properties = new List<InwOaProperty>();
   propertyNode = (InwGUIPropertyNode2)_nwOpState.GetGUIPropertyNode(path, true);

   foreach (InwGUIAttribute2 attribute in propertyNode.GUIAttributes())
   {
      try
      {
         string classUsername = attribute.ClassUserName;
         if (classUsername.Equals(attributeName))
         {
            foreach (InwOaProperty p in attribute.Properties())
            {
               InwOaProperty property =
                  (InwOaProperty)_nwOpState.ObjectFactory(nwEObjectType.eObjectType_nwOaProperty, null, null);

               property.UserName = p.UserName;
               property.value = p.value;

               properties.Add(property);
            }
            break;
         }
      }
      catch (Exception e)
      {
         System.Windows.Forms.MessageBox.Show(e.Message + e.StackTrace);
      }
   }
}

In this example, it could be assumed that everything would work as expected. Indeed, debugging this section of code, where the Garbage collector is less optimized, all could work as expected. However, 'propertyNode' is last used with the call to GUIAttributes(). Once this call has completed, the .NET Garbage Collector would be allowed to delete propertyNode as it is no longer used. In the case of the InwGUIPropertyNode2 class, the removal of propertyNode also deletes the attributes, because of the underlying functionality of the COM API, making calls such as 'attribute.Properties()' throw exceptions.

This problem is not uncommon with .NET programs using COM components and there are a number of solutions to the problem. The simplest solution here is to call GC.KeepAlive(propertyNode) after the loop on GUIAttributes(). KeepAlive, a function of the Garbage Collector class (GC), lets the Garbage Collector know that propertyNode is ineligable for Garbage Collection from the point of declaration to the point where KeepAlive is called.

The fixed code could therefor look like this:

CopyUsing GC.KeepAlive

foreach (InwOaPath path in sel.Paths())
{
   InwGUIPropertyNode2 propertyNode;
   List<InwOaProperty> properties = new List<InwOaProperty>();
   propertyNode = (InwGUIPropertyNode2)_nwOpState.GetGUIPropertyNode(path, true);

   foreach (InwGUIAttribute2 attribute in propertyNode.GUIAttributes())
   {
      try
      {
         string classUsername = attribute.ClassUserName;
         if (classUsername.Equals(attributeName))
         {
            foreach (InwOaProperty p in attribute.Properties())
            {
               InwOaProperty property =
                  (InwOaProperty)_nwOpState.ObjectFactory(nwEObjectType.eObjectType_nwOaProperty, null, null);

               property.UserName = p.UserName;
               property.value = p.value;

               properties.Add(property);
            }
            break;
         }
      }
      catch (Exception e)
      {
         System.Windows.Forms.MessageBox.Show(e.Message + e.StackTrace);
      }
   }
   //Call here to keep propertyNode 'alive' through the inner
   GC.KeepAlive(propertyNode);
}

This class facilitates using the COM API with the .NET API by providing some methods to aid working between the two APIs.

The State property of the class provides access to the COM API equivalent of MainDocument as can be seen in the example at the beginning of this chapter.

There are also methods for converting between the .NET API ModelItem and the COM API's InwOaPath as well as converting to/from ModelItemCollection and InwOpSelection.