I am not sure I understand what is the problem.. Your code works perfectly with minor changes.
I replaced your cForm with one that has a textbox1 that displays all the properties of the objects you double click. It should help you identify/discover any issues. Alll you should have to do is add a winform to your project and drag a textbox1 on it:
Keep me posted where is your code failing exactly, because this works for me. Also, I am using AutoCAD 2013, it should be easy to replace document code relevant to 2012 or earlier.
Imports acOp = Autodesk.AutoCAD.Interop
Public db As Database = HostApplicationServices.WorkingDatabase
Public ed As Editor = activeDoc.Editor
Public ReadOnly Property ThisDrawing() As AcadDocument
Get
Return DocumentExtension.GetAcadDocument(Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument)
End Get
End Property
Private acDoc As acOp.AcadDocument
Private handlerAdded As Boolean = False
Private cForm As New frmMassStraight
Public Sub eventDoubleClick()
Try
If handlerAdded = False Then
MgdAcApplication.SetSystemVariable("DBLCLKEDIT", 0)
If acDoc Is Nothing Then
acDoc = CType(ThisDrawing, Autodesk.AutoCAD.Interop.AcadDocument)
AddHandler acDoc.BeginDoubleClick, AddressOf callback_DoubleClick
End If
handlerAdded = True
End If
Catch ex As Autodesk.AutoCAD.Runtime.Exception
MsgBox(ex.Message, MsgBoxStyle.Critical)
Finally
MgdAcApplication.SetSystemVariable("DBLCLKEDIT", 1)
End Try
End Sub
Private Sub DisplayError(ByVal msg As String)
ed.WriteMessage(vbLf + msg)
cForm.TextBox1.Text += msg + vbCrLf
MgdAcApplication.ShowModalDialog(cForm)
End Sub
Private Sub callback_DoubleClick(ByVal PickPoint As Object)
Dim prmtSel As PromptSelectionResult = activeDoc.Editor.GetSelection()
Dim msg As String = ""
Using docLock As DocumentLock = activeDoc.LockDocument()
If prmtSel.Status <> PromptStatus.OK Then
DisplayError(String.Format("ERROR: prmtSel.Status= {0}", prmtSel.Status))
Return
End If
If prmtSel.Value.Count <> 1 Then
DisplayError(String.Format("ERROR: prmtSel.Value.Count={0}", prmtSel.Value.Count))
Return
End If
Dim id As Autodesk.AutoCAD.DatabaseServices.ObjectId = prmtSel.Value(0).ObjectId
Try
Using acTrans As Autodesk.AutoCAD.DatabaseServices.Transaction = _
activeDoc.TransactionManager.StartTransaction()
Dim dbObj As Autodesk.AutoCAD.DatabaseServices.DBObject = _
acTrans.GetObject(id, Autodesk.AutoCAD.DatabaseServices.OpenMode.ForWrite)
Dim ent As Autodesk.AutoCAD.DatabaseServices.Entity = _
TryCast(dbObj, Autodesk.AutoCAD.DatabaseServices.Entity)
cForm.Text = ent.GetType().ToString()
For Each p As System.Reflection.PropertyInfo In ent.GetType().GetProperties()
Try
Dim displStr As String = String.Format(" {0}: '{1}'", p.Name, p.GetValue(ent, Nothing))
cForm.TextBox1.Text += displStr + vbCrLf
Catch
Dim msgStr As String = String.Format("ERR: '{0}' p='{1}'", Err.Description, p.ToString)
ed.WriteMessage(vbLf + msgStr)
cForm.TextBox1.Text += msgStr + vbCrLf
End Try
Next
If ent Is Nothing Then
DisplayError(String.Format("ERROR: ent={0}", ent))
Return
Else
Dim blockRef As Autodesk.AutoCAD.DatabaseServices.BlockReference = _
TryCast(ent, Autodesk.AutoCAD.DatabaseServices.BlockReference)
If blockRef Is Nothing Then
DisplayError(String.Format("ERROR: blockRef={0}", blockRef))
Return
Else
activeDoc.Editor.WriteMessage(blockRef.BlockName)
End If
End If
acTrans.Commit()
End Using
Catch ex As Autodesk.AutoCAD.Runtime.Exception
Dim msgStr As String = String.Format("EX: '{0}'", ex.ToString)
ed.WriteMessage(vbLf + msgStr)
cForm.TextBox1.Text += msgStr + vbCrLf
Catch
Dim msgStr As String = String.Format("ERR: '{0}'", Err.Description)
ed.WriteMessage(vbLf + msgStr)
cForm.TextBox1.Text += msgStr + vbCrLf
End Try
End Using
MgdAcApplication.ShowModalDialog(cForm)
End Sub
' Component for displaying the Mass Straight Conveyor form
<CommandMethod("mst")> _
Public Sub massStraight()
Try
' Call this to override default block dblclk event handler
eventDoubleClick()
Catch ex As Autodesk.AutoCAD.Runtime.Exception
MsgBox(ex.Message, MsgBoxStyle.Critical)
End Try
End Sub
