RichEditControl event handler, prompting to save upon form close with nothing has changed - vb.net

Question

Having an issue when closing the form and nothing has changed, it still prompts to save the form. We have a form that has multiple controls. There are a few lookup combo boxes with data. They select their data and then click a button called "view". View then brings up a few textboxes and combo boxes etc and populates with data. There is also a RichEditControl that also gets loaded. After all the data is loaded in the load event. The last line is to call the following method to set event handlers for all controls. If something has changed after that then prompt to save upon form closing.
customFunc.AddDirtyEvent(Me)
The issue is and we have test if there is no richtextbox, it works. If the only control on a form is a RichEditControl, it always prompts to save no matter what, even if nothing has changed upon load. I noticed if you have a form that has a RichEditControl, and it gets populated upon form load. Even if you call the eventhandler after that, it still prompts you to save BUT if you add the eventhandler call in the form shown event, it seems to work as it doesn't set the dirty bit again. Its almost like the events are queue at the end of the form load event. But then it goes to the shown event, the call is made there and the dirty bit doesn't get reset back to true.
Issue is in our case, we can't use a shown event, because we have a button "view" that loads all the data and populates a RichEditControl. So even if we add the event handlers after the data gets loaded in the same method, it always goes back to set the dirty bit to true. We need to somehow keep the dirty bit to false after this, so if there is no changes and they just want to view data don't prompt to save upon form closing. Below is my code.
If customFunc.IsDirty = True Then
Dim dr As DialogResult = MessageBox.Show("Do you want save changes before leaving?", "Closing Mud Report", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Warning, MessageBoxDefaultButton.Button2)
If dr = Windows.Forms.DialogResult.Yes Then
SimpleButtonSave.PerformClick()
ElseIf dr = Windows.Forms.DialogResult.Cancel Then
e.Cancel = True
End If
End If
Private Sub SetIsDirty(ByVal sender As System.Object, ByVal e As System.EventArgs)
is_Dirty = True
End Sub
Public Sub AddDirtyEvent(ByVal ctrl As Control)
For Each c As Control In ctrl.Controls
If TypeOf c Is RichEditControl Then
Dim rtb As RichEditControl = CType(c, RichEditControl)
AddHandler rtb.RtfTextChanged, AddressOf SetIsDirty
End If
If c.Controls.Count > 0 Then
AddDirtyEvent(c)
End If
Next
End Sub

Answer 1

In your SetIsDirty method check for RichEditControl.Modified property.
Here is example:
Private Sub SetIsDirty(ByVal sender As System.Object, ByVal e As System.EventArgs)
If TypeOf sender Is RichEditControl Then
Dim rtb As RichEditControl = CType(sender, RichEditControl)
is_Dirty = is_Dirty OrElse rtb.Modified
Else
is_Dirty = True
End If
End Sub