VB.net Need Text Box to Only Accept Maximum and Minimum Numbers - vb.net

Question

Imports System.Drawing
Imports System.Text.RegularExpressions
Imports System.Windows.Forms
Module Module1
Public Enum ValidationType
MaxMin = 1
End Enum
Public Sub AssignValidation(ByRef CTRL As TextBox, ByVal Validation_Type As ValidationType, Min As Double, Max As Double)
Dim txt As TextBox = CTRL
Select Case Validation_Type
Case ValidationType.MaxMin
AddHandler txt.TextChanged, AddressOf MaximumMinimum
End Select
End Sub
Public Sub MaximumMinimum(ByVal sender As Object, ByVal e As System.EventArgs)
Dim NO As TextBox = sender
If Val(NO.Text) < Min Then
NO.Focus()
ElseIf Val(NO.Text) > Max Then
NO.Focus()
End If
End Sub
End Module
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
AssignValidation(Me.TextBox1, ValidationType.MaxMin,Zo.Min,Zo.Max)
End Sub
I have question about that code. If I have several textboxes and all textboxes will have different maximum and minimum values, those minimum and maximum values are declared in the module for each textbox, then how can I add these values to that code?
Because that code shows at a moment Min=0 and Max=0 but actually I have different values.

Answer 1

You can use a Dictionary of Object to Tuple to store the min/max. (You can add more to the tuple if you want for example a custom error message or colors, etc.)
Option Strict On
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
AssignValidation(Me.TextBox1, ValidationType.MaxMin, 5, 10)
AssignValidation(Me.TextBox2, ValidationType.MaxMin, 0, 5)
End Sub
End Class
Module Module1
Private ranges As New Dictionary(Of Object, Tuple(Of Double, Double))()
Public Enum ValidationType
MaxMin = 1
End Enum
Public Sub AssignValidation(CTRL As TextBox, Validation_Type As ValidationType, Min As Double, Max As Double)
Select Case Validation_Type
Case ValidationType.MaxMin
If Not ranges.ContainsKey(CTRL) Then ranges.Add(CTRL, New Tuple(Of Double, Double)(Min, Max))
AddHandler CTRL.TextChanged, AddressOf MaximumMinimum
End Select
End Sub
Public Sub MaximumMinimum(sender As Object, e As System.EventArgs)
Dim textbox = DirectCast(sender, TextBox)
Dim value As Double
If Double.TryParse(textbox.Text, value) Then
' SUCCESS - parsed as Double
If value >= ranges(sender).Item1 AndAlso value <= ranges(sender).Item2 Then
' SUCCESS - within min and max
Else
' FAIL - outside min or max
textbox.Focus() ' what does this even do?
End If
Else
' FAIL - did not parse as Double
MessageBox.Show(textbox.Text)
End If
End Sub
End Module
* Edited to use pre .NET 7.0 Tuple syntax

Answer 2

Why not use the Validating event for each text box and the error provider.
Private err As New ErrorProvider()
Private Sub TextBox1_Validating(sender As Object, e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating
If TextBox1.Text = "" Then
e.Cancel = True
err.SetError(TextBox1, "This text box cannot be blank.")
Else
err.Clear()
`enter code here`End If
End Sub