GridView怎么分页

初学GridView分页 有首页 上一页 下一页 尾页 文本框输入页数 点GO按钮  跪求后台代码怎么写？？aspx页面
 
<asp:gridview id="GridView1" runat="server" allowpaging="True" pagesize="10" autogeneratecolumns="False"   onpageindexchanging="GridView1_PageIndexChanging">
             <columns>
                 <asp:boundfield datafield="CompanyName" headertext="CompanyName" sortexpression="CompanyName" />
                 <asp:boundfield datafield="ContactTitle" headertext="ContactTitle" sortexpression="ContactTitle" />
                 <asp:boundfield datafield="Phone" headertext="Phone" sortexpression="Phone" />
                 <asp:boundfield datafield="Fax" headertext="Fax" sortexpression="Fax" />
                 <asp:boundfield datafield="ContactName" headertext="ContactName" sortexpression="ContactName" />
             </columns>
                        <pagertemplate>
                         <table width="100%">
                           <tr>
                             <td style="text-align:right">
                             第<asp:Label id="lblPageIndex" runat="server" text='<%# ((GridView)Container.Parent.Parent).PageIndex + 1   %>' />页
                                 共/<asp:Label id="lblPageCount" runat="server" text='<%# ((GridView)Container.Parent.Parent).PageCount   %>' />页 
                                 <asp:linkbutton id="btnFirst" runat="server" causesvalidation="False" commandargument="First" commandname="Page" text="首页" />
                               <asp:linkbutton id="btnPrev" runat="server" causesvalidation="False" commandargument="Prev" commandname="Page" text="上一页" />
                              <asp:linkbutton id="btnNext" runat="server" causesvalidation="False" commandargument="Next" commandname="Page" text="下一页" />                          
                              <asp:linkbutton id="btnLast" runat="server" causesvalidation="False" commandargument="Last" commandname="Page" text="尾页" />                                            
                              <asp:textbox id="txtNewPageIndex" runat="server" width="20px" text='<%# ((GridView)Container.Parent.Parent).PageIndex + 1   %>' />
                              <asp:linkbutton id="btnGo" runat="server" causesvalidation="False" commandargument="-1" commandname="Page" text="GO" />>