VB.Net/GUI/Error Provider

Use ErrorProvider

<source lang="vbnet"> Imports System Imports System.Data Imports System.Windows.Forms Imports System.Drawing Public Class MainClass

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

End Class Public Class Form1

   Private Sub txtZip_Validating(ByVal sender As Object, _
    ByVal e As System.ruponentModel.CancelEventArgs) Handles txtZip.Validating
       If Not (txtZip.Text Like "#####") Then
           ErrorProvider1.SetError(txtZip, "Invalid ZIP code format")
       Else
           ErrorProvider1.SetError(txtZip, "")
       End If
   End Sub

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 Overloads 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.txtState = New System.Windows.Forms.TextBox
       Me.txtZip = New System.Windows.Forms.TextBox
       Me.ErrorProvider1 = New System.Windows.Forms.ErrorProvider(Me.ruponents)
       CType(Me.ErrorProvider1, System.ruponentModel.ISupportInitialize).BeginInit()
       Me.SuspendLayout()
       "
       "txtState
       "
       Me.txtState.Location = New System.Drawing.Point(88, 104)
       Me.txtState.Name = "txtState"
       Me.txtState.Size = New System.Drawing.Size(40, 20)
       Me.txtState.TabIndex = 9
       "
       "txtZip
       "
       Me.txtZip.Location = New System.Drawing.Point(192, 104)
       Me.txtZip.Name = "txtZip"
       Me.txtZip.Size = New System.Drawing.Size(40, 20)
       Me.txtZip.TabIndex = 11
       "
       "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(292, 130)
       Me.Controls.Add(Me.txtZip)
       Me.Controls.Add(Me.txtState)
       Me.Name = "Form1"
       Me.Text = "UseErrorProvider"
       CType(Me.ErrorProvider1, System.ruponentModel.ISupportInitialize).EndInit()
       Me.ResumeLayout(False)
       Me.PerformLayout()
   End Sub
   Friend WithEvents txtZip As System.Windows.Forms.TextBox
   Friend WithEvents txtState As System.Windows.Forms.TextBox
   Friend WithEvents ErrorProvider1 As System.Windows.Forms.ErrorProvider

End Class

      </source>