How to get values from a dialog form in VB.NET? - vb.net

Question

I have a "frmOptions" form with a textbox named "txtMyTextValue" and a button named "btnSave" to save and close the form when it's clicked,
then, I'm showing this dialog form "frmOptions" when a button "btnOptions" is clicked on the main form "frmMain", like this
Private Sub btnOptions_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOptions.Click
ShowOptionsForm()
End Sub
Private Sub ShowOptionsForm()
Dim options = New frmOptions
options.ShowDialog()
End Sub
How can I get in the main form "frmMain" the value inserted in the textbox "txtMyTextValue" when the "btnSave" is clicked?

Answer 1

You want to capture the information from the dialog only if the result is OK (user presses Save instead of Cancel or closes the dialog some other way), so do this:
Private Sub ShowOptionsForm()
Dim options = New frmOptions
' Did the user click Save?
If options.ShowDialog() = Windows.Forms.DialogResult.OK Then
' Yes, so grab the values you want from the dialog here
Dim textBoxValue As String = options.txtMyTextValue.Text
End If
End Sub
Now inside of your dialog form, you need to set the result Windows.Forms.DialogResult.OK when the user clicks the button that corresponds to the OK action of the dialog form, like this:
Public Class frmOptions
Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
' Set the result to pass back to the form that called this dialog
Me.DialogResult = Windows.Forms.DialogResult.OK
End Sub
End Class

Answer 2

The simplest method is to add a public property to the frmOptions form that returns an internal string declared at the global level of the frmOptions
Dim strValue As String
Public Property MyStringValue() As String
Get
Return strValue
End Get
End Property
Then, when your user clicks the OK button to confirm its choices you copy the value of the textbox to the internal variable
Private Sub cmdOK_Click(sender As Object, e As System.EventArgs) Handles cmdOK.Click
strValue = txtMyTextValue.Text
End Sub
Finally in the frmMain you use code like this to retrieve the inserted value
Private Sub ShowOptionsForm()
Using options = New frmOptions()
if DialogResult.OK = options.ShowDialog() Then
Dim value = options.MyStringValue
End If
End Using
End Sub
I prefer to avoid direct access to the internal controls of the frmOptions, a property offer a indirection that could be used to better validate the inputs given by your user.

Answer 3

You can use Events to take care of this. With this approach the Settings Form does not have to be Modal and the user can click the Save Button at any time.
In frmOptions:
'You can expand the signature to take more than just a single String.
Friend Event SavedOptions(ByVal strData As String)
Private Sub btnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSave.Click
RaiseEvent SavedOptions(txtMyTextValue.Text)
End Sub
In frmMain:
Private Sub ShowOptionsForm()
Dim options = New frmOptions
AddHandler options.SavedOptions, AddressOf OnOptionsSave
options.ShowDialog()
End Sub
Private Sub OnOptionsSave(ByVal strData As String)
'Or whatever you want to do on frmMain with Options Data.
MsgBox(strData)
End Sub

Answer 4

You can access the value from the frmOptions instance. However, this breaks the law of demeter.
You should expose the value with a property within your class.
Public Class frmOptions
Public ReadOnly Property MyTextValue As String
Get
Return Me.txtMyTextValue.Text
End Get
End Property
End Class
Then you can access the value:
Private Sub ShowOptionsForm()
Dim options = New frmOptions
Dim frmOptionTextValue As String
Dim frmOptionsDiagResult As DialogResult
frmOptionsDiagResult = options.ShowDialog()
If frmOptionsDiagResult = Windows.Forms.DialogResult.OK Then
frmOptionTextValue = options.MyTextValue
Else
'...
End If
End Sub
Finally, if you are using a Dialog then make sure to set the Dialog Result for the button.