Error 0x800A01A8 thrown after Undo in PowerPoint

Question

My code has to merge selected shapes into one by 1. finding the topmost shape 2. making combined string 3. putting string to the topmost shape 4. deleting other shapes. It works fine, but if user does UNDO (Ctrl+Z), and error 0x800A01A8 is thrown. Any
ideas?
'_firstCoordinate stores .Top coordinates, _allCoordinates finds shapes through these coordinates
Dim _firstCoordinate As New List(Of Single)
Dim _allCoordinates As New Dictionary(Of Single, PPT.Shape)
'Omitted code for initiatization, sorting, etc
'====
'====
'This works fine
If _allCoordinates(_firstCoordinate(0)).HasTextFrame Then
If _allCoordinates(_firstCoordinate(0)).TextFrame.HasText Then
_combinedString = _allCoordinates(_firstCoordinate(0)).TextFrame.TextRange.Text + Environment.NewLine
Else
_combinedString = ""
End If
Else
_exitMarker = True
End If
'Make combined text string and delete shapes
For i = 1 To _firstCoordinate.Count - 1 Step 1
If _allCoordinates(_firstCoordinate(i)).HasTextFrame Then
'This line throws error (.TextFrame.HasText)
If _allCoordinates(_firstCoordinate(i)).TextFrame.HasText Then
_combinedString = _combinedString + _allCoordinates(_firstCoordinate(i)).TextFrame.TextRange.Text + Environment.NewLine
_allCoordinates(_firstCoordinate(i)).Delete()
System.Runtime.InteropServices.Marshal.ReleaseComObject(_allCoordinates(_firstCoordinate(i))) : _allCoordinates(_firstCoordinate(i)) = Nothing
End If
End If
Next

Answer 1

Hi Herrpuqq,
Thanks for posting in MSDN forum.
According to the description, you got the error when you does UNDO action after you combine the string into anther shape.
However, based on the code, it got error when the code is running? Did I misunderstood? Would you mind sharing more detail about the issue?
Since it seems the issue relative to the code, would you mind sharing a workable demo to help us reproduce this issue?
You can upload it via OneDrive and please remove the sensitive information before you uploading.
Regards & Fei
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The code merges strings and then deletes empty shapes (keeps the upmost only). I get error when I try to access TextFrame.HasText for the shape that were previously deleted. .HasTextFrame and .Top works fine. 
This is the entire sub
Dim _firstCoordinate As New List(Of Single)
Dim _allCoordinates As New Dictionary(Of Single, PPT.Shape)
_allCoordinates.Clear()
Dim i As Integer
Dim _combinedString As String
Dim _exitMarker As Boolean = False
'Make list
Dim shp As PPT.Shape
For Each shp In Globals.ThisAddIn.Application.ActiveWindow.Selection.ShapeRange
If _allCoordinates.ContainsKey(shp.Top) Then
shp.Top = shp.Top - 1
End If
_firstCoordinate.Add(shp.Top)
_allCoordinates.Add(shp.Top, shp)
Next
'Sort list
_firstCoordinate.Sort()
'This works fine
If _allCoordinates(_firstCoordinate(0)).HasTextFrame Then
If _allCoordinates(_firstCoordinate(0)).TextFrame.HasText Then
_combinedString = _allCoordinates(_firstCoordinate(0)).TextFrame.TextRange.Text + Environment.NewLine
Else
_combinedString = ""
End If
Else
_exitMarker = True
End If
If _exitMarker Then
MsgBox("Unsuitable topmost shape")
Exit Sub
End If
'Make combined text string and delete shapes
For i = 1 To _firstCoordinate.Count - 1 Step 1
If _allCoordinates(_firstCoordinate(i)).HasTextFrame Then
'This line throws error (.TextFrame.HasText)
If _allCoordinates(_firstCoordinate(i)).TextFrame.HasText Then
_combinedString = _combinedString + _allCoordinates(_firstCoordinate(i)).TextFrame.TextRange.Text + Environment.NewLine
_allCoordinates(_firstCoordinate(i)).Delete()
System.Runtime.InteropServices.Marshal.ReleaseComObject(_allCoordinates(_firstCoordinate(i))) : _allCoordinates(_firstCoordinate(i)) = Nothing
End If
End If
Next
'Put to first shape
_allCoordinates(_firstCoordinate(0)).TextFrame.TextRange.Text = _combinedString