Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
 
Imports Autodesk.AutoCAD.Interop
Imports Autodesk.AutoCAD.Interop.Common

Public Class Class1
    '为命令 AddCOMEvent 和 RemoveCOMEvent定义公有变量
    Dim acAppCom As AcadApplication

    <CommandMethod("AddCOMEvent")> _
    Public Sub AddCOMEvent()
        '将appComBeginFileDrop 注册到Application.AcadApplication.BeginFileDrop
        acAppCom = Application.AcadApplication
        AddHandler acAppCom.BeginFileDrop, AddressOf appComBeginFileDrop
    End Sub

    <CommandMethod("RemoveCOMEvent")> _
    Public Sub RemoveCOMEvent()
        '解除注册
        RemoveHandler acAppCom.BeginFileDrop, AddressOf appComBeginFileDrop
        acAppCom = Nothing
    End Sub

    Public Sub appComBeginFileDrop(ByVal strFileName As String, _
                                   ByRef bCancel As Boolean)
        '当DWG文件被托放到AutoCAD上时，显示对话框确认是否打开。
        If System.Windows.Forms.MessageBox.Show("AutoCAD 将要打开:" & _
                                strFileName & vbLf & _
                                "你确定要打开它吗？", _
                                "DWG 文件拖放", _
                                System.Windows.Forms.MessageBoxButtons.YesNo) = _
          System.Windows.Forms.DialogResult.No Then
            bCancel = True
        End If
    End Sub

End Class