Question

I’ve re-created the _DAcadApplicationEvents interface from an AutoCAD interop .dll using .NET Reflector, and have my code working for AutoCAD 2010. The problem is that I need this to be compatible with AutoCAD 2006 all the way up to 2012 and forward. I am running .NET 4.0, and am therefore using Embed Interop Type set to true to make sure my Application object resolves properly to runtime without needing reflection invoke methods, but I can’t seem to find a way to get the event interface working without hard-coding in the GUID (which is assembly specific).

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Here is the custom interface I created from the original AutoDesk.AutoCAD.Interop.dll:

    <ComImport(), Guid("1F893620-C96D-4361-BBAF-A61D4144B7F8"), TypeLibType(CShort(&H1010))>
    Public Interface _DAcadApplicationEventsClone
        <MethodImpl(MethodImplOptions.InternalCall, MethodCodeType:=MethodCodeType.Runtime), DispId(1)>
        Sub SysVarChanged(<[In](), MarshalAs(UnmanagedType.BStr)> ByVal SysvarName As String, <[In](),
                          MarshalAs(UnmanagedType.Struct)> ByVal newVal As Object)

        <MethodImpl(MethodImplOptions.InternalCall, MethodCodeType:=MethodCodeType.Runtime), DispId(8)>
        Sub BeginQuit(<[In](), Out()> ByRef Cancel As Boolean)
    End Interface

The Application object gets created in this manner:

Public Application As Object

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Application = Marshal.GetActiveObject("AutoCAD.Application")

Next I am connecting to the cloned interface using IConnectionPoint:

Dim acGUID As New Guid(GetInterfaceGUID())

Dim acConnectionPoint As ComTypes.IConnectionPoint = Nothing
TryCast(Application, ComTypes.IConnectionPointContainer).FindConnectionPoint(acGUID, acConnectionPoint)

Dim acSinkCookie As Integer
acConnectionPoint.Advise(Me, acSinkCookie)

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As you can see, I’m running a function called ‘GetInterfaceGUID’ to dynamically search for the right GUID depending on what version of AutoCAD is installed on the system. However, if the GUID returned doesn’t match the hard-coded GUID on the interface, it won’t work anyway. I’ve tried different methods of reflection to work with a System._ComObject, and this is the only method that I’ve gotten to even come close. I feel like I’m fairly close to succeeding, and would appreciate any input at this point. Thanks in advance.

-Locke

Answer 1

As you found, the AutoCAD COM Interop is version and even bitness (32bit/64bit) dependant. Why not use the AutoCAD .NET Application Events to get rid of these trouble as follows?

using System;
using System.Text;
using System.Linq;
using System.Xml;
using System.Reflection;
using System.ComponentModel;
using System.Collections;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Media.Imaging;
using System.Windows.Forms;

using System.IO;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.EditorInput;

using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Windows;

using AcadApplication = Autodesk.AutoCAD.ApplicationServices.Application;
using AcadDocument = Autodesk.AutoCAD.ApplicationServices.Document;
using AcadWindows = Autodesk.AutoCAD.Windows;

namespace AcadNetAddinByVS2010
{
    public class AppEvents1
    {
        bool mSuppressMsgOutput = false;

        void OptionalMessageOutput(EventArgs obj, string eventName)
        {
            if (!mSuppressMsgOutput)
            {
                string msg = string.Format("Info about the {0} event:{1}", eventName, Environment.NewLine);

                PropertyInfo[] piArr = obj.GetType().GetProperties();
                foreach (PropertyInfo pi in piArr)
                {
                    string attValue = pi.GetValue(obj, null).ToString();
                    msg += string.Format("\t{0}: {1}{2}", pi.Name, attValue, Environment.NewLine);
                }

                MessageBox.Show(msg, "Event: " + eventName, MessageBoxButtons.OK, MessageBoxIcon.Information);
                System.Diagnostics.Debug.Write(msg);
            }
        }

        public void Register()
        {
            AcadApplication.SystemVariableChanging += AppEvent_SystemVariableChanging_Handler;
            AcadApplication.SystemVariableChanged += AppEvent_SystemVariableChanged_Handler;
            AcadApplication.QuitWillStart += AppEvent_QuitWillStart_Handler;
            AcadApplication.QuitAborted += AppEvent_QuitAborted_Handler;
            AcadApplication.PreTranslateMessage += AppEvent_PreTranslateMessage_Handler;
            AcadApplication.LeaveModal += AppEvent_LeaveModal_Handler;
            AcadApplication.Idle += AppEvent_Idle_Handler;
            AcadApplication.EnterModal += AppEvent_EnterModal_Handler;
            AcadApplication.DisplayingOptionDialog += AppEvent_DisplayingOptionDialog_Handler;
            AcadApplication.DisplayingDraftingSettingsDialog += AppEvent_DisplayingDraftingSettingsDialog_Handler;
            AcadApplication.DisplayingCustomizeDialog += AppEvent_DisplayingCustomizeDialog_Handler;
            AcadApplication.BeginQuit += AppEvent_BeginQuit_Handler;

        }

        public void UnRegister()
        {
            AcadApplication.SystemVariableChanging -= AppEvent_SystemVariableChanging_Handler;
            AcadApplication.SystemVariableChanged -= AppEvent_SystemVariableChanged_Handler;
            AcadApplication.QuitWillStart -= AppEvent_QuitWillStart_Handler;
            AcadApplication.QuitAborted -= AppEvent_QuitAborted_Handler;
            AcadApplication.PreTranslateMessage -= AppEvent_PreTranslateMessage_Handler;
            AcadApplication.LeaveModal -= AppEvent_LeaveModal_Handler;
            AcadApplication.Idle -= AppEvent_Idle_Handler;
            AcadApplication.EnterModal -= AppEvent_EnterModal_Handler;
            AcadApplication.DisplayingOptionDialog -= AppEvent_DisplayingOptionDialog_Handler;
            AcadApplication.DisplayingDraftingSettingsDialog -= AppEvent_DisplayingDraftingSettingsDialog_Handler;
            AcadApplication.DisplayingCustomizeDialog -= AppEvent_DisplayingCustomizeDialog_Handler;
            AcadApplication.BeginQuit -= AppEvent_BeginQuit_Handler;

        }

        public void AppEvent_BeginQuit_Handler(object sender, EventArgs e)
        {
            OptionalMessageOutput(e, "BeginQuit");

        }

        public void AppEvent_DisplayingCustomizeDialog_Handler(object sender, TabbedDialogEventArgs e)
        {
            OptionalMessageOutput(e, "DisplayingCustomizeDialog");

        }

        public void AppEvent_DisplayingDraftingSettingsDialog_Handler(object sender, TabbedDialogEventArgs e)
        {
            OptionalMessageOutput(e, "DisplayingDraftingSettingsDialog");

        }

        public void AppEvent_DisplayingOptionDialog_Handler(object sender, TabbedDialogEventArgs e)
        {
            OptionalMessageOutput(e, "DisplayingOptionDialog");

        }

        public void AppEvent_EnterModal_Handler(object sender, EventArgs e)
        {
            OptionalMessageOutput(e, "EnterModal");

        }

        public void AppEvent_Idle_Handler(object sender, EventArgs e)
        {
            OptionalMessageOutput(e, "Idle");

        }

        public void AppEvent_LeaveModal_Handler(object sender, EventArgs e)
        {
            OptionalMessageOutput(e, "LeaveModal");

        }

        public void AppEvent_PreTranslateMessage_Handler(object sender, PreTranslateMessageEventArgs e)
        {
            OptionalMessageOutput(e, "PreTranslateMessage");

        }

        public void AppEvent_QuitAborted_Handler(object sender, EventArgs e)
        {
            OptionalMessageOutput(e, "QuitAborted");

        }

        public void AppEvent_QuitWillStart_Handler(object sender, EventArgs e)
        {
            OptionalMessageOutput(e, "QuitWillStart");

        }

        public void AppEvent_SystemVariableChanged_Handler(object sender, Autodesk.AutoCAD.ApplicationServices.SystemVariableChangedEventArgs e)
        {
            OptionalMessageOutput(e, "SystemVariableChanged");

        }

        public void AppEvent_SystemVariableChanging_Handler(object sender, Autodesk.AutoCAD.ApplicationServices.SystemVariableChangingEventArgs e)
        {
            OptionalMessageOutput(e, "SystemVariableChanging");

        }

    }
}

Here is the event registration code in the chosen IExtensionApplication implementation by the way:

#region Namespaces

using System;
using System.Text;
using System.Linq;
using System.Xml;
using System.Reflection;
using System.ComponentModel;
using System.Collections;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Media.Imaging;
using System.Windows.Forms;
using System.Drawing;
using System.IO;

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Windows;

using AcadApplication = Autodesk.AutoCAD.ApplicationServices.Application;
using AcadDocument = Autodesk.AutoCAD.ApplicationServices.Document;
using AcadWindows = Autodesk.AutoCAD.Windows;

#endregion

namespace AcadNetAddinByVS2010
{
    public class ExtApp : IExtensionApplication
    {
        #region IExtensionApplication Members

        public void Initialize()
        {
            //TODO: add code to run when the ExtApp initializes. Here are a few examples:
            //          Checking some host information like build #, a patch or a particular Arx/Dbx/Dll;
            //          Creating/Opening some files to use in the whole life of the assembly, e.g. logs;
            //          Adding some ribbon tabs, panels, and/or buttons, when necessary;
            //          Loading some dependents explicitly which are not taken care of automatically;
            //          Subscribing to some events which are important for the whole session;
            //          Etc.

            mAppEvents1.Register();
        }

        public void Terminate()
        {
            //TODO: add code to clean up things when the ExtApp terminates. For example:
            //          Closing the log files;
            //          Deleting the custom ribbon tabs/panels/buttons;
            //          Unloading those dependents;
            //          Un-subscribing to those events;
            //          Etc.

            mAppEvents1.UnRegister();
        }

        #endregion

        AppEvents1 mAppEvents1 = new AppEvents1();
    }
}