当DataGrid同时具有分页和排序功能时应注意在重新绑定数据源时，MyDataGrid.CurrentPageIndex=0;
下面给实现以上功能的原码，也就不多缀了aspx中包含有DataGrid和控制其数据源变化的dropdownlist
DataGrid代码
  <asp:datagrid id="MyDataGrid" runat="server" BorderColor="#CCCCCC" Font-Size="100%" HorizontalAlign="Center"
   AutoGenerateColumns="False" OnDeleteCommand="MyDataGrid_Delete" OnSortCommand="Sort_Grid" OnPageIndexChanged="MyDataGrid_PageIndexChanged"
   DataKeyField="ACC_NO" PagerStyle-Position="Bottom" PagerStyle-HorizontalAlign="Center" PagerStyle-Mode="NextPrev"
   PageSize="10" AllowSorting="True" AllowPaging="True" CellPadding="4" Width="100%">
   <AlternatingItemStyle BackColor="#E9E9E6"></AlternatingItemStyle>
   <HeaderStyle Font-Bold="True" Wrap="False" ForeColor="White" BackColor="#999999"></HeaderStyle>
   <Columns>
<asp:ButtonColumn Text="口" CommandName="Delete"></asp:ButtonColumn>
<asp:BoundColumn DataField="NO" SortExpression="NO" ReadOnly="True" HeaderText="序号"></asp:BoundColumn>
<asp:BoundColumn DataField="ID" SortExpression="ID" HeaderText="ID"></asp:BoundColumn>
<asp:BoundColumn DataField="NAME" SortExpression="NAME" HeaderText="名称"></asp:BoundColumn>
<asp:BoundColumn DataField="C_NAME" SortExpression="C_NAME" HeaderText="各科名称"></asp:BoundColumn>
<asp:BoundColumn DataField="FLG" SortExpression="FLG" HeaderText="项目"></asp:BoundColumn>
   </Columns>
   <PagerStyle NextPageText="下10件" PrevPageText="返回" HorizontalAlign="Center"></PagerStyle>
  </asp:datagrid>

dropdownlist代码
<asp:dropdownlist id="ddlWk" Runat="server" AutoPostBack="True" Enabled="False">
   <asp:ListItem Value="0">东京</asp:ListItem>
   <asp:ListItem Value="3">九州</asp:ListItem>
   <asp:ListItem Value="8">北海道</asp:ListItem>
   <asp:ListItem Value="9">四国</asp:ListItem>
  </asp:dropdownlist>

aspx.cs文件代码核心如下：
private void Page_Load(object sender, System.EventArgs e)
  {
   if(!IsPostBack)
   {
Session["WP"] ="0";
ddlWk_getS();
BindGrid();
   } 
  }
  private void ddlWk_getS()
  {
   switch (Session["WP"].ToString())
   {
case "0":ddlWk.SelectedIndex=0;
  break;
case "3":ddlWk.SelectedIndex=1;
  break;
case "8":ddlWk.SelectedIndex=2;
  break;
case "9":ddlWk.SelectedIndex=3;
  break;
default:ddlWk.SelectedIndex=0;
  break;
   }
  }
  protected void BindGrid()
  {
   MyDataGrid.DataSource=GetData().Tables["vCO"].DefaultView;
   MyDataGrid.DataBind();
   //COUNT.Text=MyDataGrid.Columns.Count.ToString();
  }

/// <summary>
  /// 返回Data
  /// </summary>
  ///<returns></returns>
  private DataSet GetData()
  {
   string strConn=(String) ((NameValueCollection) Context.GetConfig("system.web/database"))["strConn"];
   using (SqlConnection conn = new SqlConnection(strConn))
   {
SqlCommand cmd = new SqlCommand("sp_C",conn);
cmd.CommandType=CommandType.StoredProcedure;
cmd.Parameters.Add("@place",SqlDbType.VarChar,2);
cmd.Parameters["@place"].Value=Session["WP"].ToString();
conn.Open();

SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand=cmd;
DataSet ds=new DataSet();
da.Fill(ds,"vCO");
Count.Text="ヒット："+ds.Tables["vCO"].Rows.Count.ToString()+"件";
return ds;
   }

}
  /// <summary>
  ///从DataSet中除一
  /// </summary>
  /// <param name="sender"></param>
  /// <param name="E"></param>
  protected void MyDataGrid_Delete(Object sender, DataGridCommandEventArgs E)
  {
String strID=MyDataGrid.DataKeys[(int)E.Item.ItemIndex].ToString();
//删除操作
  }
  /// <summary>
  /// 分页操作
  /// </summary>
  /// <param name="sender"></param>
  /// <param name="e"></param>
  protected void MyDataGrid_PageIndexChanged(object source, DataGridPageChangedEventArgs e)
  {
   MyDataGrid.CurrentPageIndex=e.NewPageIndex;
   BindGrid();
  }
  /// <summary>
  /// 排序
  /// </summary>
  /// <param name="sender"></param>
  /// <param name="e"></param>
  protected void Sort_Grid(object sender, DataGridSortCommandEventArgs e)
  {
   DataView dv= new DataView(GetData().Tables["vCO"]);
   dv.Sort= e.SortExpression.ToString();
   MyDataGrid.DataSource=dv;
   MyDataGrid.DataBind();
  }

#region Web   override protected void OnInit(EventArgs e)
  {
   //   //
   InitializeComponent();
   base.OnInit(e);
  }
 
  /// <summary>  /// </summary>
  private void InitializeComponent()
  {
   this.ddlWk.SelectedIndexChanged += new System.EventHandler(this.ddlWk_SelectedIndexChanged);
   this.Load += new System.EventHandler(this.Page_Load);

}
  #endregion

private void ddlWk_SelectedIndexChanged(object sender, System.EventArgs e)
  {
   Session["WP"]=ddlWk.SelectedValue;
   MyDataGrid.CurrentPageIndex=0;//没有这一句，当该页码超出其他数据源的范围时会出错
   BindGrid();
   Response.Write( "<script language='javascript'>parent.menuframe.location.reload();</script>");
 
  }