Textboxes as array

Hello guys once again.
I have a problem to code textboxes as an array.What I mean.

I have 3 textboxes and I am trying to group them using some kind of index, so having textbox(j) instead of textbox1, textbox2, textbox3.
I would like to have something like this because i want to use some loop instructions.

I have written the following code as an example.
In brief the code is this
If textbox1 and textbox2 is numeric then textbox3="done"
Else
give a msgbox("blah....")
---------
Dim J As Integer
Dim txt As TextBox()

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
For Me.J = 0 To 1
If Not IsNumeric(txt(J).Text) Then
MsgBox("PLEASE ENTER ONLY NUMBERS!", MsgBoxStyle.Critical, "WARNING")
Else
TextBox3.Text = "done"
End If
Next J
end sub

-------------

When i run this code i get a message "NullReferenceException was unhandeled etc"

create a list(of textbox) and add each one of your textboxes to it when the form initializes...
i.e.

Code:

---


dim tbList as new list(of textbox)
tblist.add(textbox1)
tblist.add(textbox2)
tbList.add(textbox3)
'etc...

---

The first textbox added can be referenced using tbList(0), the second tbList(1), and so on

Or, put the textboxes into a container control (panel, group box, flow layout panel, etc.) and use the containers Controls collection, eg. Panel1.Controls(i)

Or, use the form's Control's collection with an OfType statement

Or, abandon textboxes and use NumericUpDown controls so that you don't need to validate and therefore don't need the loop at all!

If what you're actually trying to achieve is validation then you don't need any looping. Validation is already built into the control and the form, e.g.

vb.net Code:

Imports System.ComponentModel
 
Public Class Form1
 
    Private Sub NumericTextBox_Validating(sender As Object, e As CancelEventArgs) Handles TextBox2.Validating,
                                                                                          TextBox1.Validating
        Dim field = DirectCast(sender, TextBox)
 
        If Not Double.TryParse(field.Text, Nothing) Then
            field.SelectAll()
            field.HideSelection = False
 
            MessageBox.Show("Please enter a numeric value.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Error)
 
            field.HideSelection = False
 
            'Don't let the user leave the field until they enter valid input.
            e.Cancel = False
        End If
    End Sub
 
    Private Sub saveButton_Click(sender As Object, e As EventArgs) Handles saveButton.Click
        If Me.ValidateChildren() Then
            'All fields have passed validation so save with confidence.
        End If
    End Sub
 
End Class

The Validating even is raised when the user tries to shift focus from the TextBox and setting e.Cancel prevents that from happening. Calling ValidateChildren will raise the event on all controls so even those that have never received focus will be validated.