Check to see if selection/text was changed in form - vb.net

Question

I have a form with about 20 controls on it (ComboBox, TextBox, etc) that I have pre-loaded with data. This is being displayed to the user and gives them the capability to change any of the fields.
I do not know the best way of recognizing that changes have taken place. After some research, I found TextBox.TextChanged and setting the flag IsDirty = True or something along those lines.
I don't think this will be 100% bulletproof since the user might change the value and then go back and change it to how it was when initially loaded. I've been thinking about saving the current data to .Tag and then comparing it with the .Text that was entered when the user clicks "Cancel" to simply ask them if they'd like to save the changes.
This is my code:
Private Sub Form1_Load(ByVal sender as Object, byVal e as System.EventArgs)Handles MyBase.Load
For Each ctr as Control in me.Controls
if typeof ctr is TextBox then
ctr.tag=ctr.text
end if
Next
End Sub
This is the code for when the user clicks "Cancel":
Private Sub CmdCancel_Click (ByVal sender as Object, ByVal e As System.EventArgs) Handles CmdCancel.Click
For each ctr As Control in Me.Controls
If Typeof ctr is Textbox then
if ctr.tag.tostring <> ctr.text then
MsgBox ("Do you want to save the items", YesNo)
end if
End if
Next
End sub
Is this an effective way to do this? Can it be relied on? If anyone has any better idea, I'd love to hear it.

Answer 1

Have a look at this:
For Each txtBox In Me.Controls.OfType(Of TextBox)()
If txtBox.Modified Then
'Show message
End If
Next
EDIT
Have a look at this. This may be of interest to you if you wanted an alternative way to the .Tag property:
'Declare a dictionary to store your original values
Private _textboxDictionary As New Dictionary(Of TextBox, String)
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'You would place this bit of code after you had set the values of the textboxes
For Each txtBox In Me.Controls.OfType(Of TextBox)()
_textboxDictionary.Add(txtBox, txtBox.Text)
Next
End Sub
Then use this to find out the original value and compare to the new value:
For Each txtBox In Me.Controls.OfType(Of TextBox)()
If txtBox.Modified Then
Dim oldValue = (From kp As KeyValuePair(Of TextBox, String) In _textboxDictionary
Where kp.Key Is txtBox
Select kp.Value).First()
If oldValue.ToString() <> txtBox.Text Then
'Show message
End If
End If
Next

Answer 2

I know this already has an accepted answer, but I thought the part about checking if the actual text value has changed should be addressed. Checking modified will reveal if any changes were made to the text, but it will fail if the user, for example, adds a character and then deletes it. I think a good way to do this would be with a custom control, so here's an example of a simple control that stores the textbox's original text whenever it is changed programmatically, and has a textaltered property that can be checked to show whether or not the user's modifications actually resulted in the text being different from its original state. This way, each time you fill the textbox with data yourself, the value you set is saved. Then when you are ready, you just check the TextAltered property:
Public Class myTextBox
Inherits System.Windows.Forms.TextBox
Private Property OriginalText As String
Public ReadOnly Property TextAltered As Boolean
Get
If OriginalText.Equals(MyBase.Text) Then
Return False
Else
Return True
End If
End Get
End Property
Public Overrides Property Text As String
Get
Return MyBase.Text
End Get
Set(value As String)
Me.OriginalText = value
MyBase.Text = value
End Set
End Property
End Class