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Thread: Textboxes as array

  1. #1

    Thread Starter
    Join Date
    Sep 2010

    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"
    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")
    TextBox3.Text = "done"
    End If
    Next J
    end sub


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

  2. #2
    Still learning kebo's Avatar
    Join Date
    Apr 2004

    Re: Textboxes as array

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

    dim tbList as new list(of textbox)
    The first textbox added can be referenced using tbList(0), the second tbList(1), and so on
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    Last edited by kebo : Now. Reason: superfluous typo's

  3. #3
    PowerPoster dunfiddlin's Avatar
    Join Date
    Jun 2012

    Re: Textboxes as array

    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!
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  4. #4
    .NUT jmcilhinney's Avatar
    Join Date
    May 2005
    Sydney, Australia

    Re: Textboxes as array

    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. Code:
    1. Imports System.ComponentModel
    3. Public Class Form1
    5.     Private Sub NumericTextBox_Validating(sender As Object, e As CancelEventArgs) Handles TextBox2.Validating,
    6.                                                                                           TextBox1.Validating
    7.         Dim field = DirectCast(sender, TextBox)
    9.         If Not Double.TryParse(field.Text, Nothing) Then
    10.             field.SelectAll()
    11.             field.HideSelection = False
    13.             MessageBox.Show("Please enter a numeric value.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Error)
    15.             field.HideSelection = False
    17.             'Don't let the user leave the field until they enter valid input.
    18.             e.Cancel = False
    19.         End If
    20.     End Sub
    22.     Private Sub saveButton_Click(sender As Object, e As EventArgs) Handles saveButton.Click
    23.         If Me.ValidateChildren() Then
    24.             'All fields have passed validation so save with confidence.
    25.         End If
    26.     End Sub
    28. 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.

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