The AutoCAD COM Automation library offers some unique events that are not found in the .NET API. Registering events that are in a COM library is different than how you would initialize an event using VB or VBA. You use the VB.NET AddHandler statement or the C# += operator to reigister an event handler with the event. The event handler requires the address of the procedure in which should be called when the event is raised.
This example demonstrates how to register the BeginFileDrop event using COM interop. The BeginFileDrop event is associated with the Application object of the AutoCAD COM Automation library. Once the commands are loaded into AutoCAD, enter AddCOMEvent at the Command prompt and then drag and drop a DWG file into the drawing window. A message box will be displayed prompting you to continue. Use the RemoveCOMEvent command to remove the event handler.
Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Interop
Imports Autodesk.AutoCAD.Interop.Common
'' Global variable for AddCOMEvent and RemoveCOMEvent commands
Dim acAppCom As AcadApplication
<CommandMethod("AddCOMEvent")> _Public Sub AddCOMEvent()
'' Set the global variable to hold a reference to the application and
'' register the BeginFileDrop COM event
acAppCom = Application.AcadApplication
AddHandler acAppCom.BeginFileDrop, AddressOf appComBeginFileDrop
End Sub
<CommandMethod("RemoveCOMEvent")> _Public Sub RemoveCOMEvent()
'' Unregister the COM event handle
RemoveHandler acAppCom.BeginFileDrop, AddressOf appComBeginFileDrop
acAppCom = Nothing
End Sub
Public Sub appComBeginFileDrop(ByVal strFileName As String, _
ByRef bCancel As Boolean)
'' Display a message box prompting to continue inserting the DWG file
If System.Windows.Forms.MessageBox.Show("AutoCAD is about to load " & _strFileName & vbLf & _
"Do you want to continue loading this file?", _
"DWG File Dropped", _
System.Windows.Forms.MessageBoxButtons.YesNo) = _
System.Windows.Forms.DialogResult.No Then
bCancel = True
End If
End Sub
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Interop;
using Autodesk.AutoCAD.Interop.Common;
// Global variable for AddCOMEvent and RemoveCOMEvent commands
AcadApplication acAppCom;
[CommandMethod("AddCOMEvent")]public void AddCOMEvent()
{// Set the global variable to hold a reference to the application and
// register the BeginFileDrop COM event
acAppCom = Application.AcadApplication as AcadApplication;
acAppCom.BeginFileDrop +=
new _DAcadApplicationEvents_BeginFileDropEventHandler(appComBeginFileDrop);
}
[CommandMethod("RemoveCOMEvent")]public void RemoveCOMEvent()
{// Unregister the COM event handle
acAppCom.BeginFileDrop -=
new _DAcadApplicationEvents_BeginFileDropEventHandler(appComBeginFileDrop);
acAppCom = null;
}
public void appComBeginFileDrop(string strFileName, ref bool bCancel)
{// Display a message box prompting to continue inserting the DWG file
if (System.Windows.Forms.MessageBox.Show("AutoCAD is about to load " + strFileName +"\nDo you want to continue loading this file?",
"DWG File Dropped",
System.Windows.Forms.MessageBoxButtons.YesNo) ==
System.Windows.Forms.DialogResult.No)
{bCancel = true;
}
}
