Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows 窗体设计器生成的代码 "

    Public Sub New()
        MyBase.New()

        '该调用是 Windows 窗体设计器所必需的。
        InitializeComponent()

        '在 InitializeComponent() 调用之后添加任何初始化

    End Sub

    '窗体重写 dispose 以清理组件列表。
    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

    'Windows 窗体设计器所必需的
    Private components As System.ComponentModel.IContainer

    '注意: 以下过程是 Windows 窗体设计器所必需的
    '可以使用 Windows 窗体设计器修改此过程。
    '不要使用代码编辑器修改它。
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.SuspendLayout()
        '
        'TextBox1
        '
        Me.TextBox1.Location = New System.Drawing.Point(112, 96)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.TabIndex = 0
        Me.TextBox1.Text = ""
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(6, 14)
        Me.ClientSize = New System.Drawing.Size(292, 266)
        Me.Controls.Add(Me.TextBox1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region
    Dim str As String = ""

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        Dim num As Integer = 0
        Dim temp As String = ""
        While num < TextBox1.Text.Length
            temp += "[0-9]"
            num += 1
        End While

        If Not (TextBox1.Text Like temp) Then
            TextBox1.Text = str
            TextBox1.Focus()
        Else
            str = TextBox1.Text
        End If
    End Sub
End Class