VB.Net/GUI/TextBox Validation

TextBox Validating Event

Imports System
Imports System.Collections
Imports System.Data
Imports System.IO
Imports System.Xml.Serialization
Imports System.Windows.Forms
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Drawing.Text
Imports System.Drawing.Printing

Public Class MainClass
    Shared Sub Main()
       Dim form1 As Form = New Form1()
       Application.Run(form1) 
    End Sub
End Class


Public Class Form1
    Inherits System.Windows.Forms.Form
#Region " Windows Form Designer generated code "
    Public Sub New()
        MyBase.New()
        "This call is required by the Windows Form Designer.
        InitializeComponent()
        "Add any initialization after the InitializeComponent() call
    End Sub
    "Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents Label1 As System.Windows.Forms.Label
    "Required by the Windows Form Designer
    Private components As System.ruponentModel.Container
    "NOTE: The following procedure is required by the Windows Form Designer
    "It can be modified using the Windows Form Designer.  
    "Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.TextBox1 = New System.Windows.Forms.TextBox()
        Me.Label1 = New System.Windows.Forms.Label()
        Me.SuspendLayout()
        "
        "TextBox1
        "
        Me.TextBox1.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.TextBox1.Location = New System.Drawing.Point(48, 104)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(192, 27)
        Me.TextBox1.TabIndex = 1
        Me.TextBox1.Text = ""
        "
        "Label1
        "
        Me.Label1.Font = New System.Drawing.Font("Microsoft Sans Serif", 10.2!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Label1.Location = New System.Drawing.Point(24, 24)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(232, 48)
        Me.Label1.TabIndex = 2
        Me.Label1.Text = "Type somthing"
        "
        "Form1
        "
        Me.AutoScaleBaseSize = New System.Drawing.Size(6, 15)
        Me.ClientSize = New System.Drawing.Size(292, 268)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.Label1, Me.TextBox1})
        Me.Name = "Form1"
        Me.Text = "Key Event Examples"
        Me.ResumeLayout(False)
    End Sub
#End Region
    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
    End Sub
    Public Sub TextBox1_Validating(ByVal sender As Object, _
      ByVal e As System.ruponentModel.CancelEventArgs) _
      Handles TextBox1.Validating
        " cancel the focus shift if the textbox is empty
         MessageBox.Show("Validating")
        If TextBox1.Text.Trim = Nothing Then e.Cancel = True
    End Sub
    
End Class

TextBox validation: validate in Button click event

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Public Class MainClass
    
    Shared Sub Main()
        Dim form1 As Form = New Form1
        Application.Run(form1)

    End Sub
End Class
Public Class Form1
    Inherits System.Windows.Forms.Form
#Region " Windows Form Designer generated code "
    Public Sub New()
        MyBase.New()
        "This call is required by the Windows Form Designer.
        InitializeComponent()
        "Add any initialization after the InitializeComponent() call
    End Sub
    "Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub
    "Required by the Windows Form Designer
    Private components As System.ruponentModel.IContainer
    "NOTE: The following procedure is required by the Windows Form Designer
    "It can be modified using the Windows Form Designer.  
    "Do not modify it using the code editor.
    Friend WithEvents GroupBox1 As System.Windows.Forms.GroupBox
    Friend WithEvents Label2 As System.Windows.Forms.Label
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents txtFirstName As System.Windows.Forms.TextBox
    Friend WithEvents txtLastName As System.Windows.Forms.TextBox
    Friend WithEvents Button1 As System.Windows.Forms.Button
    Friend WithEvents errProvider As System.Windows.Forms.ErrorProvider
    Friend WithEvents txtEmail As System.Windows.Forms.TextBox
    Friend WithEvents Label3 As System.Windows.Forms.Label
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.GroupBox1 = New System.Windows.Forms.GroupBox()
        Me.Label2 = New System.Windows.Forms.Label()
        Me.Label1 = New System.Windows.Forms.Label()
        Me.txtFirstName = New System.Windows.Forms.TextBox()
        Me.txtLastName = New System.Windows.Forms.TextBox()
        Me.Button1 = New System.Windows.Forms.Button()
        Me.errProvider = New System.Windows.Forms.ErrorProvider()
        Me.txtEmail = New System.Windows.Forms.TextBox()
        Me.Label3 = New System.Windows.Forms.Label()
        Me.GroupBox1.SuspendLayout()
        Me.SuspendLayout()
        "
        "GroupBox1
        "
        Me.GroupBox1.Controls.AddRange(New System.Windows.Forms.Control() {Me.Label3, Me.txtEmail, Me.Label2, Me.Label1, Me.txtFirstName, Me.txtLastName})
        Me.GroupBox1.Location = New System.Drawing.Point(8, 8)
        Me.GroupBox1.Name = "GroupBox1"
        Me.GroupBox1.Size = New System.Drawing.Size(368, 124)
        Me.GroupBox1.TabIndex = 11
        Me.GroupBox1.TabStop = False
        "
        "Label2
        "
        Me.Label2.Location = New System.Drawing.Point(16, 52)
        Me.Label2.Name = "Label2"
        Me.Label2.Size = New System.Drawing.Size(64, 16)
        Me.Label2.TabIndex = 8
        Me.Label2.Text = "Last Name:"
        "
        "Label1
        "
        Me.Label1.Location = New System.Drawing.Point(16, 28)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(64, 16)
        Me.Label1.TabIndex = 7
        Me.Label1.Text = "First Name:"
        "
        "txtFirstName
        "
        Me.txtFirstName.Location = New System.Drawing.Point(84, 24)
        Me.txtFirstName.Name = "txtFirstName"
        Me.txtFirstName.Size = New System.Drawing.Size(152, 21)
        Me.txtFirstName.TabIndex = 4
        Me.txtFirstName.Text = ""
        "
        "txtLastName
        "
        Me.txtLastName.Location = New System.Drawing.Point(84, 48)
        Me.txtLastName.Name = "txtLastName"
        Me.txtLastName.Size = New System.Drawing.Size(152, 21)
        Me.txtLastName.TabIndex = 5
        Me.txtLastName.Text = ""
        "
        "Button1
        "
        Me.Button1.Location = New System.Drawing.Point(152, 204)
        Me.Button1.Name = "Button1"
        Me.Button1.Size = New System.Drawing.Size(76, 24)
        Me.Button1.TabIndex = 10
        Me.Button1.Text = "OK"
        "
        "txtEmail
        "
        Me.txtEmail.Location = New System.Drawing.Point(84, 84)
        Me.txtEmail.Name = "txtEmail"
        Me.txtEmail.Size = New System.Drawing.Size(152, 21)
        Me.txtEmail.TabIndex = 9
        Me.txtEmail.Text = ""
        "
        "Label3
        "
        Me.Label3.Location = New System.Drawing.Point(16, 88)
        Me.Label3.Name = "Label3"
        Me.Label3.Size = New System.Drawing.Size(64, 16)
        Me.Label3.TabIndex = 10
        Me.Label3.Text = "Email:"
        "
        "ErrorProviderValidation
        "
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 14)
        Me.ClientSize = New System.Drawing.Size(388, 238)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.GroupBox1, Me.Button1})
        Me.Font = New System.Drawing.Font("Tahoma", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Name = "ErrorProviderValidation"
        Me.Text = "ErrorProvider Validation"
        Me.GroupBox1.ResumeLayout(False)
        Me.ResumeLayout(False)
    End Sub
#End Region
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim InvalidInput As Boolean = False
        Dim ctrl As Control
        For Each ctrl In Me.GroupBox1.Controls
            If errProvider.GetError(ctrl) <> "" Then
                InvalidInput = True
                Exit For
            End If
        Next
        If InvalidInput = True Then
            MessageBox.Show("You still have invalid input.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        Else
            Me.Close()
        End If
    End Sub
End Class

TextBox validation: validate in Validating Event

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Public Class MainClass
    
    Shared Sub Main()
        Dim form1 As Form = New Form1
        Application.Run(form1)

    End Sub
End Class
Public Class Form1
    Inherits System.Windows.Forms.Form
#Region " Windows Form Designer generated code "
    Public Sub New()
        MyBase.New()
        "This call is required by the Windows Form Designer.
        InitializeComponent()
        "Add any initialization after the InitializeComponent() call
    End Sub
    "Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub
    "Required by the Windows Form Designer
    Private components As System.ruponentModel.IContainer
    "NOTE: The following procedure is required by the Windows Form Designer
    "It can be modified using the Windows Form Designer.  
    "Do not modify it using the code editor.
    Friend WithEvents GroupBox1 As System.Windows.Forms.GroupBox
    Friend WithEvents Label2 As System.Windows.Forms.Label
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents txtFirstName As System.Windows.Forms.TextBox
    Friend WithEvents txtLastName As System.Windows.Forms.TextBox
    Friend WithEvents Button1 As System.Windows.Forms.Button
    Friend WithEvents errProvider As System.Windows.Forms.ErrorProvider
    Friend WithEvents txtEmail As System.Windows.Forms.TextBox
    Friend WithEvents Label3 As System.Windows.Forms.Label
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.GroupBox1 = New System.Windows.Forms.GroupBox()
        Me.Label2 = New System.Windows.Forms.Label()
        Me.Label1 = New System.Windows.Forms.Label()
        Me.txtFirstName = New System.Windows.Forms.TextBox()
        Me.txtLastName = New System.Windows.Forms.TextBox()
        Me.Button1 = New System.Windows.Forms.Button()
        Me.errProvider = New System.Windows.Forms.ErrorProvider()
        Me.txtEmail = New System.Windows.Forms.TextBox()
        Me.Label3 = New System.Windows.Forms.Label()
        Me.GroupBox1.SuspendLayout()
        Me.SuspendLayout()
        "
        "GroupBox1
        "
        Me.GroupBox1.Controls.AddRange(New System.Windows.Forms.Control() {Me.Label3, Me.txtEmail, Me.Label2, Me.Label1, Me.txtFirstName, Me.txtLastName})
        Me.GroupBox1.Location = New System.Drawing.Point(8, 8)
        Me.GroupBox1.Name = "GroupBox1"
        Me.GroupBox1.Size = New System.Drawing.Size(368, 124)
        Me.GroupBox1.TabIndex = 11
        Me.GroupBox1.TabStop = False
        "
        "Label2
        "
        Me.Label2.Location = New System.Drawing.Point(16, 52)
        Me.Label2.Name = "Label2"
        Me.Label2.Size = New System.Drawing.Size(64, 16)
        Me.Label2.TabIndex = 8
        Me.Label2.Text = "Last Name:"
        "
        "Label1
        "
        Me.Label1.Location = New System.Drawing.Point(16, 28)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(64, 16)
        Me.Label1.TabIndex = 7
        Me.Label1.Text = "First Name:"
        "
        "txtFirstName
        "
        Me.txtFirstName.Location = New System.Drawing.Point(84, 24)
        Me.txtFirstName.Name = "txtFirstName"
        Me.txtFirstName.Size = New System.Drawing.Size(152, 21)
        Me.txtFirstName.TabIndex = 4
        Me.txtFirstName.Text = ""
        "
        "txtLastName
        "
        Me.txtLastName.Location = New System.Drawing.Point(84, 48)
        Me.txtLastName.Name = "txtLastName"
        Me.txtLastName.Size = New System.Drawing.Size(152, 21)
        Me.txtLastName.TabIndex = 5
        Me.txtLastName.Text = ""
        "
        "Button1
        "
        Me.Button1.Location = New System.Drawing.Point(152, 204)
        Me.Button1.Name = "Button1"
        Me.Button1.Size = New System.Drawing.Size(76, 24)
        Me.Button1.TabIndex = 10
        Me.Button1.Text = "OK"
        "
        "txtEmail
        "
        Me.txtEmail.Location = New System.Drawing.Point(84, 84)
        Me.txtEmail.Name = "txtEmail"
        Me.txtEmail.Size = New System.Drawing.Size(152, 21)
        Me.txtEmail.TabIndex = 9
        Me.txtEmail.Text = ""
        "
        "Label3
        "
        Me.Label3.Location = New System.Drawing.Point(16, 88)
        Me.Label3.Name = "Label3"
        Me.Label3.Size = New System.Drawing.Size(64, 16)
        Me.Label3.TabIndex = 10
        Me.Label3.Text = "Email:"
        "
        "ErrorProviderValidation
        "
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 14)
        Me.ClientSize = New System.Drawing.Size(388, 238)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.GroupBox1, Me.Button1})
        Me.Font = New System.Drawing.Font("Tahoma", 8.25!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
        Me.Name = "ErrorProviderValidation"
        Me.Text = "ErrorProvider Validation"
        Me.GroupBox1.ResumeLayout(False)
        Me.ResumeLayout(False)
    End Sub
#End Region
    Private Sub txtName_Validating(ByVal sender As Object, ByVal e As System.ruponentModel.CancelEventArgs) Handles txtFirstName.Validating, txtLastName.Validating
        If CType(sender, TextBox).Text = "" Then
            errProvider.SetError(sender, "You must enter a first and last name.")
        Else
            errProvider.SetError(sender, "")
        End If
    End Sub
End Class

Text Field Validation: five digits

Imports System
Imports System.ruponentModel
Imports System.Windows.Forms
Imports System.Data
Imports System.Configuration
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Drawing.Text
Imports System.Globalization
Imports System.Text
Imports System.Collections
Public Class MainClass
    Shared Sub Main()
        Dim myform As Form = New Form1()
        Application.Run(myform)
    End Sub
End Class
Public Class Form1
    Private Sub TextBox1_Validating(ByVal sender As Object, ByVal e As System.ruponentModel.CancelEventArgs) Handles TextBox1.Validating, TextBox2.Validating, TextBox3.Validating
        ValidateFiveDigits(DirectCast(sender, TextBox))
    End Sub
    Private Sub ValidateFiveDigits(ByVal text_box As TextBox)
        If (text_box.Text.Length <> 0) And _
        Not (text_box.Text Like "#####") _
        Then
            " Invalid. Set an error.
            ErrorProvider1.SetError(text_box, _
            text_box.Name & " must contain exactly five digits")
        Else
            " Valid. Clear the error.
            ErrorProvider1.SetError(text_box, "")
        End If
    End Sub

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        e.Cancel = True
        If IsInvalidField(TextBox1) Then 
            Exit Sub
        End If
            
        If IsInvalidField(TextBox3) Then 
            Exit Sub
        End If
        e.Cancel = False
    End Sub
    Private Function IsInvalidField(ByVal ctl As Control) As Boolean
        If ErrorProvider1.GetError(ctl).Length = 0 Then
            Return False
        Else
            MessageBox.Show(ErrorProvider1.GetError(ctl))
            ctl.Focus()
            Return True
        End If
    End Function
End Class
<Global.Microsoft.VisualBasic.rupilerServices.DesignerGenerated()> _
Partial Public Class Form1
    Inherits System.Windows.Forms.Form
    "Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing AndAlso components IsNot Nothing Then
            components.Dispose()
        End If
        MyBase.Dispose(disposing)
    End Sub
    "Required by the Windows Form Designer
    Private components As System.ruponentModel.IContainer
    "NOTE: The following procedure is required by the Windows Form Designer
    "It can be modified using the Windows Form Designer.  
    "Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.ruponents = New System.ruponentModel.Container
        Me.Label1 = New System.Windows.Forms.Label
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.TextBox2 = New System.Windows.Forms.TextBox
        Me.Label2 = New System.Windows.Forms.Label
        Me.TextBox3 = New System.Windows.Forms.TextBox
        Me.Label3 = New System.Windows.Forms.Label
        Me.ErrorProvider1 = New System.Windows.Forms.ErrorProvider(Me.ruponents)
        CType(Me.ErrorProvider1, System.ruponentModel.ISupportInitialize).BeginInit()
        Me.SuspendLayout()
        "
        "Label1
        "
        Me.Label1.AutoSize = True
        Me.Label1.Location = New System.Drawing.Point(8, 8)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(56, 13)
        Me.Label1.TabIndex = 0
        Me.Label1.Text = "Five Digits"
        "
        "TextBox1
        "
        Me.TextBox1.Location = New System.Drawing.Point(72, 8)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(80, 20)
        Me.TextBox1.TabIndex = 1
        "
        "TextBox2
        "
        Me.TextBox2.Location = New System.Drawing.Point(72, 32)
        Me.TextBox2.Name = "TextBox2"
        Me.TextBox2.Size = New System.Drawing.Size(80, 20)
        Me.TextBox2.TabIndex = 3
        "
        "Label2
        "
        Me.Label2.AutoSize = True
        Me.Label2.Location = New System.Drawing.Point(8, 32)
        Me.Label2.Name = "Label2"
        Me.Label2.Size = New System.Drawing.Size(56, 13)
        Me.Label2.TabIndex = 2
        Me.Label2.Text = "Five Digits"
        "
        "TextBox3
        "
        Me.TextBox3.Location = New System.Drawing.Point(72, 56)
        Me.TextBox3.Name = "TextBox3"
        Me.TextBox3.Size = New System.Drawing.Size(80, 20)
        Me.TextBox3.TabIndex = 5
        "
        "Label3
        "
        Me.Label3.AutoSize = True
        Me.Label3.Location = New System.Drawing.Point(8, 56)
        Me.Label3.Name = "Label3"
        Me.Label3.Size = New System.Drawing.Size(56, 13)
        Me.Label3.TabIndex = 4
        Me.Label3.Text = "Five Digits"
        "
        "ErrorProvider1
        "
        Me.ErrorProvider1.ContainerControl = Me
        "
        "Form1
        "
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(210, 83)
        Me.Controls.Add(Me.TextBox3)
        Me.Controls.Add(Me.Label3)
        Me.Controls.Add(Me.TextBox2)
        Me.Controls.Add(Me.Label2)
        Me.Controls.Add(Me.TextBox1)
        Me.Controls.Add(Me.Label1)
        Me.Name = "Form1"
        Me.Text = "Deferred Validation"
        CType(Me.ErrorProvider1, System.ruponentModel.ISupportInitialize).EndInit()
        Me.ResumeLayout(False)
        Me.PerformLayout()
    End Sub
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents TextBox2 As System.Windows.Forms.TextBox
    Friend WithEvents Label2 As System.Windows.Forms.Label
    Friend WithEvents TextBox3 As System.Windows.Forms.TextBox
    Friend WithEvents Label3 As System.Windows.Forms.Label
    Friend WithEvents ErrorProvider1 As System.Windows.Forms.ErrorProvider
End Class