如何在网格视图中保留控件的状态，并在 asp.net 中分页

我在此网格视图中添加了文本框的验证，但此验证仅适用于 GridView 的当前页面（它不适用于 GridView 的上一页和下一页）。

<asp:GridView ID="Grd1" runat ="server" Width ="100%" AllowPaging ="true" pagesize="5">
  <Columns>
    <asp:BoundField HeaderText="Name" DataField="NM" ItemStyle-Width="300px" HeaderStyle-Width="300px" HeaderStyle-Wrap="false" ItemStyle-Wrap="false" />
    <asp:TemplateField HeaderText="Size (GB)">
      <ItemTemplate>
        <asp:TextBox ID="txtSize" runat="server" Width="100px"></asp:TextBox>
      </ItemTemplate>
    </asp:TemplateField>
  </Columns>
</asp:GridView>
<asp:Button ID="btnAdd" runat="server" Text="Save" OnClick="btnAdd_Click" />
<script language="javascript" type="text/javascript">
    function IsValidateAdd() {
        if (validateGridTextBox() == false)
            { return false; }
    }
    function validateGridTextBox() {
        var flag = false;
        var dropdowns = new Array(); //Create array to hold all the dropdown lists.
        var gridview = document.getElementById('<%=Grd1.ClientID %>'); //grvDMODetails is the id of ur gridview.
        dropdowns = gridview.getElementsByTagName('input'); //Get all dropdown lists contained in Grd1.            
        for (var i = 0; i < dropdowns.length; i++) {
            if (dropdowns.item(i).value != "") //If dropdown has no selected value
            {
                flag = true;
            }
            else 
            {
                flag = false;
                break;
            }
        }
        if (flag == false) 
        {
            alert('Please enter Table Size.');
            return flag;
        }
</script>

代码隐藏：

btnAddDM.Attributes.Add("onclick", "return IsValidateAdd();");