vb.net - enable/disable a button depending on user input - vb.net

Question

As I'm putting the finishing touches on my program I'm having some troubles.
Theres several user inputs and a submit button, once the inputs has been filled I wish to enable the submit button, else the button should be disabled. This is what I have:
Private Sub ButtonControl(sender As System.Object, e As System.EventArgs) Handles Input1.Validated
If Input1.Text = "" Then
ButtonSubmit.Enabled = False
ElseIf Input1.Text <> "" Then
ButtonSubmit.Enabled = True
End If
End Sub
The thing is it disables nomatter what and then it doesnt enable when my input is filed

Answer 1

Your code will work if you have another control that can receive the focus. Control Validation occurs on the loss of focus. If you need to have just one focusable item active you will need to use either KeyPress, KeyDown or Textchanged events to enable your button, also make sure that the CausesValidation property of your TextBox is true.
I would also make the method more generic so you could call it from multiple textbox's by using the sender object to access the textbox that raised the event. Also if you have a True/False condition you only need to do the comparison in the first if statement and then you just use an else not an elseif.
for example:
Private Sub ButtonControl(sender As System.Object, e As System.EventArgs) Handles Input1.Validated
If DirectCast(sender, TextBox).Text = "" Then
ButtonSubmit.Enabled = False
Else
ButtonSubmit.Enabled = True
End If
End Sub
You can also use the String.IsNullOrWhiteSpace Method to check if just spaces have been entered if you are using the 4.0 framework or above. Like this TextChanged EventHandler.
Private Sub ButtonControl(sender As Object, e As EventArgs) Handles Input1.TextChanged
If String.IsNullOrWhiteSpace(DirectCast(sender, TextBox).Text) Then
ButtonSubmit.Enabled = False
Else
ButtonSubmit.Enabled = True
End If
End Sub

Answer 2

You are going to need to use the TextBox "TextChanged" event, and be sure to set each Textbox AutoPostback="True". You can use an UpdatePanel to make the postbacks that occur on each Textbox you wish to validate less obnoxious to your end-user.
So, your textbox (if you have many, make sure they all have the OnTextChanged="ValidateForm":
<asp:TextBox ID="Input1" runat="server" OnTextChanged="Validate_TextChanged" />
Inside your textchanged ("ValidateForm") event (which each Textbox is attached to), one quick to implement route to do would just be
' Validation inside this event
Protected Sub Validate_TextChanged(sender As Object, e As EventArgs)
if Input1.text <> "" AndAlso Input2.text <> "" AndAlso ' ...etc.
End Sub
If you go the route of the UpdatePanel, you may find this useful.

Answer 3

This is the kind of thing I would do:
Private Sub TextBoxes_TextChanged( _
ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles _
TextBox1.TextChanged, _
TextBox2.TextChanged, _
TextBox3.TextChanged
Dim textBoxes = { TextBox1, TextBox2, TextBox3 }
Button1.Enabled = textBoxes.All(Function (tb) tb.Text <> "")
End Sub
You can then add as many text boxes in to the textBoxes array as you need to check. Just make sure that the text boxes to the Handles list.

Answer 4

Private Sub TextBox1_TextChanged(sender As System.Object, e As System.EventArgs) Handles TextBox1.TextChanged
If TextBox1.Text.Length > 0 Then
Me.Button1.Enabled = True
Else
Me.Button1.Enabled = False
End If
End Sub

Answer 5

Do that code in the Input1_TextChanged event
This is what I did and worked:
Dim CheckInput1 As Boolean
Private Sub Input1_TextChanged(sender As Object, e As EventArgs) Handles Input1.TextChanged, Input1.Enter
CheckInput1 = True
If Input1.Text = "" Then
CheckInput1 = False
End If
If CheckInput1 = False Then
ButtonSubmit.Enabled = False
ElseIf CheckInput1 = True Then
ButtonSubmit.Enabled = True
End If
End Sub
There must be a more efficient code that this but I think this solves your problem.