UpdateProgress 和GridView自动分页

为了更好的显示加载的效果，，asp.net ajax控件里有UpdateProgress非常常用，就可以实现这个功能。
default.aspx设计代码如下：
 <form id="form1" runat="server">
    <div>
       <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>   
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
        <asp:Label ID="Label2" runat="server" Text="请输入用户名"></asp:Label><input type="text" id="text2" /><asp:Button
            ID="Button2" runat="server" Text="查询" onclick="Button1_Click" />
         <asp:UpdateProgress ID="UpdateProgress1" runat="server">
        <ProgressTemplate>
        正在加载数据.............
        </ProgressTemplate>
        </asp:UpdateProgress>
            <asp:GridView ID="GridView1" runat="server" Width="347px" AllowPaging="True"
                AutoGenerateColumns="False" PageSize="2"
                onpageindexchanging="GridView1_PageIndexChanging">
                <Columns>
                    <asp:BoundField HeaderText="编号" DataField="id"/>
                    <asp:BoundField HeaderText="用户名" DataField="UserName"/>
                    <asp:BoundField HeaderText="密码"  DataField="PassWord"/>
                    <asp:BoundField HeaderText="类别"  DataField="unit"/>
                </Columns>
            </asp:GridView>
        </ContentTemplate>       
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="Button2" EventName="Click" />
            </Triggers>
        </asp:UpdatePanel>
    </div>
    </form>

default.cs:

protected void Button1_Click(object sender, EventArgs e)
    {
        System.Threading.Thread.Sleep(3000);
        databind();
    }
    public void databind()
    {
        string sql = "SELECT [id], [UserName], [PassWord], [unit] FROM [UserTable]";
        string con = "Data Source=.;Initial Catalog=OfficeData;Persist Security Info=True;User ID=sa;Password=1234";
        SqlConnection mycon = new SqlConnection(con);
        mycon.Open();
        SqlDataAdapter mydt = new SqlDataAdapter(sql, mycon);
        DataSet ds = new DataSet();
        mydt.Fill(ds);

        GridView1.DataSource = ds;
        GridView1.DataBind();
        mycon.Close();
    }
    protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        GridView1.PageIndex = e.NewPageIndex;
        databind();
    }