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Application Events

Namespace: Autodesk.AutoCAD.ApplicationServices
Assembly: acmgd.dll

Overview

The Application class exposes application-level events that fire when documents are created, opened, closed, or when the application state changes. These are global events that apply across all documents.

Key Concept: Application events monitor the AutoCAD application itself, not individual documents. Use these for application-wide operations like managing document collections or responding to system-level changes.

Key Events

Event Description
DocumentCreated Fires when a new document is created
DocumentToBeDestroyed Fires before a document is destroyed
DocumentDestroyed Fires after a document is destroyed
DocumentActivated Fires when a document becomes active
DocumentToBeActivated Fires before a document becomes active
DocumentToBeDeactivated Fires before a document is deactivated
DocumentBecameCurrent Fires when a document becomes current
BeginQuit Fires before AutoCAD quits
QuitAborted Fires when quit is aborted
QuitWillStart Fires when quit will start
SystemVariableChanged Fires when a system variable changes
SystemVariableWillChange Fires before a system variable changes

Common Usage Patterns

1. Document Lifecycle Monitoring

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.Runtime;

public class ApplicationEventMonitor
{
    public void RegisterEvents()
    {
        Application.DocumentManager.DocumentCreated += OnDocumentCreated;
        Application.DocumentManager.DocumentToBeDestroyed += OnDocumentToBeDestroyed;
        Application.DocumentManager.DocumentDestroyed += OnDocumentDestroyed;
    }
    
    public void UnregisterEvents()
    {
        Application.DocumentManager.DocumentCreated -= OnDocumentCreated;
        Application.DocumentManager.DocumentToBeDestroyed -= OnDocumentToBeDestroyed;
        Application.DocumentManager.DocumentDestroyed -= OnDocumentDestroyed;
    }
    
    private void OnDocumentCreated(object sender, DocumentCollectionEventArgs e)
    {
        Editor ed = e.Document.Editor;
        ed.WriteMessage($"\n>>> Document Created: {e.Document.Name}");
    }
    
    private void OnDocumentToBeDestroyed(object sender, DocumentCollectionEventArgs e)
    {
        Editor ed = e.Document.Editor;
        ed.WriteMessage($"\n>>> Document Will Be Destroyed: {e.Document.Name}");
    }
    
    private void OnDocumentDestroyed(object sender, DocumentDestroyedEventArgs e)
    {
        // Note: Document is already destroyed, can't access Editor
        System.Diagnostics.Debug.WriteLine($"Document Destroyed: {e.FileName}");
    }
}

[CommandMethod("STARTAPPMON")]
public void StartApplicationMonitoring()
{
    ApplicationEventMonitor monitor = new ApplicationEventMonitor();
    monitor.RegisterEvents();
    
    Application.DocumentManager.MdiActiveDocument.Editor.WriteMessage(
        "\nApplication event monitoring started");
}

2. Document Activation Tracking

public class DocumentActivationTracker
{
    private int _activationCount = 0;
    
    public void Start()
    {
        Application.DocumentManager.DocumentActivated += OnDocumentActivated;
        Application.DocumentManager.DocumentToBeActivated += OnDocumentToBeActivated;
        Application.DocumentManager.DocumentToBeDeactivated += OnDocumentToBeDeactivated;
    }
    
    private void OnDocumentToBeActivated(object sender, DocumentCollectionEventArgs e)
    {
        Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
        ed.WriteMessage($"\n>>> Will Activate: {e.Document.Name}");
    }
    
    private void OnDocumentActivated(object sender, DocumentCollectionEventArgs e)
    {
        _activationCount++;
        Editor ed = e.Document.Editor;
        ed.WriteMessage($"\n>>> Activated: {e.Document.Name} (Count: {_activationCount})");
    }
    
    private void OnDocumentToBeDeactivated(object sender, DocumentCollectionEventArgs e)
    {
        Editor ed = e.Document.Editor;
        ed.WriteMessage($"\n>>> Will Deactivate: {e.Document.Name}");
    }
}

3. Auto-Save on Document Switch

public class AutoSaveOnSwitch
{
    public void Start()
    {
        Application.DocumentManager.DocumentToBeDeactivated += OnDocumentToBeDeactivated;
    }
    
    private void OnDocumentToBeDeactivated(object sender, DocumentCollectionEventArgs e)
    {
        Document doc = e.Document;
        
        // Check if document has unsaved changes
        if (doc.Database.HasSaveVersionInfo)
        {
            try
            {
                // Auto-save before switching
                doc.Database.SaveAs(doc.Name, true, DwgVersion.Current, doc.Database.SecurityParameters);
                doc.Editor.WriteMessage("\n>>> Auto-saved before switching documents");
            }
            catch (System.Exception ex)
            {
                doc.Editor.WriteMessage($"\n>>> Auto-save failed: {ex.Message}");
            }
        }
    }
}

4. System Variable Change Monitoring

public class SysVarMonitor
{
    public void Start()
    {
        Application.SystemVariableWillChange += OnSysVarWillChange;
        Application.SystemVariableChanged += OnSysVarChanged;
    }
    
    private void OnSysVarWillChange(object sender, SystemVariableChangingEventArgs e)
    {
        Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
        ed.WriteMessage($"\n>>> SysVar Will Change: {e.Name}");
        ed.WriteMessage($"\n    Current Value: {Application.GetSystemVariable(e.Name)}");
    }
    
    private void OnSysVarChanged(object sender, SystemVariableChangedEventArgs e)
    {
        Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
        ed.WriteMessage($"\n>>> SysVar Changed: {e.Name}");
        ed.WriteMessage($"\n    New Value: {Application.GetSystemVariable(e.Name)}");
    }
}

5. Application Quit Handler

public class QuitHandler
{
    public void Start()
    {
        Application.QuitWillStart += OnQuitWillStart;
        Application.QuitAborted += OnQuitAborted;
        Application.BeginQuit += OnBeginQuit;
    }
    
    private void OnBeginQuit(object sender, EventArgs e)
    {
        System.Diagnostics.Debug.WriteLine(">>> AutoCAD is beginning to quit");
        
        // Perform cleanup operations
        CleanupResources();
    }
    
    private void OnQuitWillStart(object sender, EventArgs e)
    {
        System.Diagnostics.Debug.WriteLine(">>> AutoCAD quit will start");
    }
    
    private void OnQuitAborted(object sender, EventArgs e)
    {
        System.Diagnostics.Debug.WriteLine(">>> AutoCAD quit was aborted");
    }
    
    private void CleanupResources()
    {
        // Close log files, save settings, etc.
    }
}

6. Multi-Document Statistics

public class DocumentStatistics
{
    private int _totalCreated = 0;
    private int _totalDestroyed = 0;
    private int _currentOpen = 0;
    
    public void Start()
    {
        Application.DocumentManager.DocumentCreated += OnDocumentCreated;
        Application.DocumentManager.DocumentDestroyed += OnDocumentDestroyed;
    }
    
    private void OnDocumentCreated(object sender, DocumentCollectionEventArgs e)
    {
        _totalCreated++;
        _currentOpen++;
        
        e.Document.Editor.WriteMessage("\n╔════════════════════════════════╗");
        e.Document.Editor.WriteMessage("\n║   DOCUMENT STATISTICS          ║");
        e.Document.Editor.WriteMessage("\n╠════════════════════════════════╣");
        e.Document.Editor.WriteMessage($"\n║ Total Created:  {_totalCreated,14} ║");
        e.Document.Editor.WriteMessage($"\n║ Total Destroyed: {_totalDestroyed,13} ║");
        e.Document.Editor.WriteMessage($"\n║ Currently Open:  {_currentOpen,13} ║");
        e.Document.Editor.WriteMessage("\n╚════════════════════════════════╝");
    }
    
    private void OnDocumentDestroyed(object sender, DocumentDestroyedEventArgs e)
    {
        _totalDestroyed++;
        _currentOpen--;
        
        System.Diagnostics.Debug.WriteLine($"Document destroyed. Current open: {_currentOpen}");
    }
}

Best Practices

  1. Application-wide only: Use for cross-document operations
  2. Always unregister: Critical for application events
  3. Minimal processing: Keep handlers very fast
  4. Thread-safe: Application events may fire on different threads
  5. Careful with Document access: Some events fire when documents are unavailable

Common Patterns

Pattern 1: Document Lifecycle

Application.DocumentManager.DocumentCreated += OnCreated;
Application.DocumentManager.DocumentDestroyed += OnDestroyed;

Pattern 2: Activation Tracking

Application.DocumentManager.DocumentActivated += OnActivated;
Application.DocumentManager.DocumentToBeDeactivated += OnDeactivated;

Pattern 3: Application Cleanup

Application.BeginQuit += (s, e) => {
    // Cleanup resources
};

Related Classes

See Also