Out-of-Process Versus In-Process (.NET)

When you develop a new application, it can either run in or out-of-process. The AutoCAD .NET API is designed to run in-process only, which is different from the ActiveX Automation library which can be used in or -out-of-process.

• In-process applications are designed to run in the same process space as the host application. In this case, a DLL assembly is loaded into AutoCAD which is the host application.
• Out-of-process applications do not run in the same space as the host application. These applications are often built as stand-alone executables.

If you need to create a stand-alone application to drive AutoCAD, it is best to create an application that uses the CreateObject and GetObject methods to create a new instance of an AutoCAD application or return one of the instances that is currently running. Once a reference to an AcadApplication is returned, you can then load your in-process .NET application into AutoCAD by using the SendCommand method that is a member of the ActiveDocument property of the AcadApplication.

As an alternative to executing your .NET application in-process, could use COM interop for your application.

C# Example

using System;
using System.Runtime.InteropServices;
 
using Autodesk.AutoCAD.Interop;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
 
[CommandMethod("ConnectToAcad")]
public static void ConnectToAcad()
{
 
  AcadApplication acAppComObj = null;
  const string strProgId = "AutoCAD.Application.26.0";
 
  // Get a running instance of AutoCAD
  try
  {
      acAppComObj = (AcadApplication)Marshal.GetActiveObject(strProgId);
  }
  catch // An error occurs if no instance is running
  {
      try
      {
          // Create a new instance of AutoCAD
          acAppComObj = (AcadApplication)Activator.CreateInstance(Type.GetTypeFromProgID(strProgId), true);
      }
      catch
      {
          // If an instance of AutoCAD is not created then message and exit
          System.Windows.Forms.MessageBox.Show("Instance of 'AutoCAD.Application'" +
                                               " could not be created.");
 
          return;
      }
  }
 
  // Display the application and return the name and version
  acAppComObj.Visible = true;
  System.Windows.Forms.MessageBox.Show("Now running " + acAppComObj.Name + 
                                       " version " + acAppComObj.Version);
 
  // Get the active document
  AcadDocument acDocComObj;
  acDocComObj = acAppComObj.ActiveDocument;
 
  // Optionally, load your assembly and start your command or if your assembly
  // is demandloaded, simply start the command of your in-process assembly.
  acDocComObj.SendCommand("(command " + (char)34 + "NETLOAD" + (char)34 + " " +
                          (char)34 + "c:/myapps/mycommands.dll" + (char)34 + ") ");
 
  acDocComObj.SendCommand("MyCommand ");
}