<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />

protected void Button1_Click(object sender,EventArgs e)
{
   int n = Convert.ToInt32(TextBox1.Text);
   int b = 0;
   while (n > 0)
   {
      b = b * 10;
      b = b + n % 10;
      n = n / 10;
   }
   Response.Write("得到的结果：" + b);
}