.NET (Core and Framework)

'preserve existing values for re-creation of DefaultConstraint
'NOTE: AColumn is the column we are working with and Size is the new size to set.
Dim DName As String = ""
Dim DText As String = ""
Dim DefaultConstraintWasThere As Boolean = False

'remove DefaultConstraint if it exists
If AColumn.DefaultConstraint IsNot Nothing Then
  DefaultConstraintWasThere = True
  DName = AColumn.DefaultConstraint.Name
  DText = AColumn.DefaultConstraint.Text
  AColumn.DefaultConstraint.Drop()
  'tried doing various "Alter"s here but none work,
  'citing that the DefaultConstraint's properties cannot be accessed.
End If

'make the desired change to the column property
AColumn.DataType.MaximumLength = Size

'recreate the DefaultConstraint if there was one
If DefaultConstraintWasThere Then
  Try
    'error is occurring here
    AColumn.AddDefaultConstraint(DName)
    AColumn.DefaultConstraint.Text = DText
  Catch ex As Exception
    Stop
  End Try
End If

Exception Message: External component has thrown an exception.
Stack Trace:   at System.Windows.Forms.UnsafeNativeMethods.GetOpenFileName(OPENFILENAME_I ofn)
   at System.Windows.Forms.OpenFileDialog.RunFileDialog(OPENFILENAME_I ofn)
   at System.Windows.Forms.FileDialog.RunDialog(IntPtr hWndOwner)
   at System.Windows.Forms.CommonDialog.ShowDialog(IWin32Window owner)
   at System.Windows.Forms.CommonDialog.ShowDialog()
   at FirstTimeUser.frmGatherPersInfo.btnLoad_Click(Object sender, EventArgs e)


Exception Message: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Stack Trace:   at System.Windows.Forms.UnsafeNativeMethods.IntDestroyWindow(HandleRef hWnd)
   at System.Windows.Forms.UnsafeNativeMethods.DestroyWindow(HandleRef hWnd)
   at System.Windows.Forms.NativeWindow.DestroyHandle()
   at System.Windows.Forms.Control.DestroyHandle()
   at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
   at System.Windows.Forms.Form.ShowDialog()
   at MyHealtheFile.modMain.main()

private void btnOK_Click(object sender, EventArgs e)
{
DisableForm();
Object obj = GetObjFromUI();

BackgroundWorker saveAsWorker = new BackgroundWorker();
saveAsWorker.DoWork += new DoWorkEventHandler(saveAsWorker_DoWork);
saveAsWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(saveAsWorker_RunWorkerCompleted);
saveAsWorker.RunWorkerAsync(obj);
}

void saveAsWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// Check if we should invoke
if (InvokeRequired)
{
// Invoke
Invoke(new MyEventHandler(MyObject_MyEvent), new object[] { sender, e });
}
else{
// Update UI here.
}
}