VB.Net Tutorial/GUI/ErrorProvider

ErrorProvider

Imports System.Windows.Forms
public class DeferredValidation
   public Shared Sub Main
        Application.Run(New Form1)
   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
        If (TextBox1.Text.Length <> 0) And Not (TextBox1.Text Like "##") _
        Then
            ErrorProvider1.SetError(TextBox1, TextBox1.Name & " must contain exactly two digits")
        Else
            ErrorProvider1.SetError(TextBox1, "")
        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
        If IsInvalidField(TextBox3) Then Exit Sub
        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

Get error from ErrorProvider

Imports System.Windows.Forms
public class DeferredValidation
   public Shared Sub Main
        Application.Run(New Form1)
   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
        If (TextBox1.Text.Length <> 0) And Not (TextBox1.Text Like "##") _
        Then
            ErrorProvider1.SetError(TextBox1, TextBox1.Name & " must contain exactly two digits")
        Else
            ErrorProvider1.SetError(TextBox1, "")
        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
        If IsInvalidField(TextBox3) Then Exit Sub
        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