四位整数逆序：

Public Class Form1

    Private Sub TextBox1_KeyPress(ByVal sender As Object,ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        Dim n,a,b,c,d,m As Integer

        If Asc(e.KeyChar) = 13 Then
            n = Val(TextBox1.Text)
            a = n Mod 10 '个位
            b = n \ 10 Mod 10 '十位
            c = n \ 100 Mod 10 '百位
            d = n \ 1000
            m = a * 1000 + b * 100 + c * 10 + d
            Label2.Text = "逆序后整数为：" & m
        End If


    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        If Not IsNumeric(TextBox1.Text) Then
            MsgBox("输入有非数字字符,请重新输入","数据检验")
            TextBox1.Text = ""
            TextBox1.Focus()
        End If
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub
End Class