Prevent an erase event from happening

[benjamin-cabrera]

I have this code that monitor the events and generate a TXT file.

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

public class ObjectEvents
{
    private static string logFilePath = "AutoCAD_Events_Log.txt"; // Path to the log file

    [CommandMethod("RegisterDbEvents")]
    public void RegisterDbEvents()
    {
        Document doc = Application.DocumentManager.MdiActiveDocument;
        Database db = doc.Database;

        db.ObjectAppended += new ObjectEventHandler(Db_ObjectAppended);
        db.ObjectModified += new ObjectEventHandler(Db_ObjectModified);
        db.ObjectErased += new ObjectErasedEventHandler(Db_ObjectErased);

        // Clear the log file when registering new events
        if (File.Exists(logFilePath))
        {
            File.WriteAllText(logFilePath, string.Empty);
        }

        LogEvent("Database event handlers have been registered.");
    }

    // Unregisters handlers for database events
    [CommandMethod("UnregisterDbEvents")]
    public void UnregisterDbEvents()
    {
        Document doc = Application.DocumentManager.MdiActiveDocument;
        Database db = doc.Database;

        db.ObjectAppended -= new ObjectEventHandler(Db_ObjectAppended);
        db.ObjectModified -= new ObjectEventHandler(Db_ObjectModified);
        db.ObjectErased -= new ObjectErasedEventHandler(Db_ObjectErased);

        LogEvent("Database event handlers have been unregistered.");
    }

    private void Db_ObjectAppended(object sender, ObjectEventArgs e)
    {
        LogEvent("An object has been appended to the database. Type: " + e.DBObject.GetType().Name);
    }

    private void Db_ObjectModified(object sender, ObjectEventArgs e)
    {
        LogEvent("An object has been modified in the database. Type: " + e.DBObject.GetType().Name);
    }

    private void Db_ObjectErased(object sender, ObjectErasedEventArgs e)
    {
        string message = e.Erased ? "An object has been erased from the database." : "An object has been unerased in the database.";
        LogEvent(message);
    }

    private void LogEvent(string message)
    {
        using (StreamWriter sw = File.AppendText(logFilePath))
        {
            sw.WriteLine($"{System.DateTime.Now}: {message}");
        }
    }
}

It generates a file like this

2024/04/25 11:06:49: An object has been modified in the database. Type: Xrecord
2024/04/25 11:06:49: An object has been modified in the database. Type: Xrecord
2024/04/25 11:06:49: An object has been erased from the database.
2024/04/25 11:06:49: An object has been modified in the database. Type: BlockTableRecord
2024/04/25 11:06:49: An object has been erased from the database.
2024/04/25 11:06:49: An object has been erased from the database.
2024/04/25 11:06:49: An object has been erased from the database.

It identified an erase event but is there a way to prevent/stop/block that event from happening? Thank you.

[ActivistInvestor · Accepted solution]

You can use an ObjectOverrule for that. See this blog post