Sort e Paging no GridView após FilterExpression não funciona

Olá,

estou iniciando no ASP.NET e comecei a testar algumas coisas.

Obs:

. estou tentando montar o grid pelo código e não pela toolbox.

. estou usando ajax-enabled website

. estou usando accessdatasource

Primeiramente, monto meu grid no .aspx:

<asp:AccessDataSource ID="AccessDataSource1" runat="server" DataFile="~/banco.mdb"></asp:AccessDataSource>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">

 <ContentTemplate>
 <asp:TextBox ID="TextBox1" runat="server" OnTextChanged="TextBox1_TextChanged" AutoPostBack="true"></asp:TextBox>
 <asp:MultiView ID="MultiView1" runat="server" ActiveViewIndex="0">
 <asp:View ID="ViewCliente" runat="server">
 <asp:GridView ID="GridViewCliente" runat="server" Width="100%"></asp:GridView>
 </asp:View>
 </asp:MultiView>
 </ContentTemplate>
 </asp:UpdatePanel>

Após, crio minha função de filtro genérica para poder usar em outras tabelas e a atribuo ao textbox:

private void filtraGrid(AccessDataSource datasource, GridView grid, string filtro)
{

 datasource.FilterExpression = "nome like '%" + filtro + "%'";
 grid.DataBind();
	}

protected void TextBox1_TextChanged(object sender, EventArgs e)
{

 filtraGrid(AccessDataSource1,GridViewCliente,TextBox1.Text);
	}

Minha Page_Load:

protected void Page_Load(object sender, EventArgs e)
{

 AccessDataSource1.SelectCommand = "select id_cliente,nome,contato,tel,email from CLIENTE order by NOME,CONTATO";
 AccessDataSource1.DeleteCommand = "delete from CLIENTE where ID_CLIENTE = @id_cliente";
 AccessDataSource1.InsertCommand = "insert into CLIENTE (nome) values ('"+ TextBox1.Text +"')";
 AccessDataSource1.FilterExpression = "";

 MontaGridview(GridViewCliente, "ID,Nome,Contato,Tel,E-mail", "id_cliente,nome,contato,tel,email", "id_cliente");

 GridViewCliente.DataSourceID = "AccessDataSource1";

	}

e a função de montagridview:

public void MontaGridview(GridView grid, string campos, string valores, string datakeynames)
{
//limpa o grid

 grid.Columns.Clear();

 //da split nos campos e valores
 char[] splitter = new char[] { ',' };
 string[] campo = campos.Split(splitter);
 string[] valor = valores.Split(splitter);
 //define o datakeyname
 string[] datakeyname = new string[] { datakeynames };

 //adiciona as colunas no grid
 for (int t = 0; t < campo.Length; t++)
 {
 BoundField coluna = new BoundField();
 coluna.HeaderText = campo[t];
 coluna.DataField = valor[t];
 coluna.SortExpression = valor[t];
 if(datakeynames == valor[t])
 {
 coluna.InsertVisible = false;
 coluna.ReadOnly = true;
 }
 grid.Columns.Add(coluna);
 }

 //cria a coluna de delete
 CommandField delete = new CommandField();
 delete.DeleteImageUrl = "~/icons/delete.gif";
 delete.ButtonType = ButtonType.Image;
 delete.DeleteText = "Del";
 delete.ShowDeleteButton = true;
 grid.Columns.Add(delete);

 //define o key do grid
 grid.DataKeyNames = datakeyname;

 //define estilos
 grid.FooterStyle.BackColor = corHtml("#5D7B9D");
 grid.FooterStyle.Font.Bold = true;
 grid.FooterStyle.ForeColor = corHtml("#FFFFFF");
 grid.RowStyle.BackColor = corHtml("#F7F6F3");
 grid.RowStyle.ForeColor = corHtml("#333333");
 grid.EditRowStyle.BackColor = corHtml("#999999");
 grid.SelectedRowStyle.BackColor = corHtml("#E2DED6");
 grid.SelectedRowStyle.Font.Bold = true;
 grid.SelectedRowStyle.ForeColor = corHtml("#333333");
 grid.PagerStyle.BackColor = corHtml("#284775");
 grid.PagerStyle.ForeColor = corHtml("#FFFFFF");
 grid.PagerStyle.HorizontalAlign = HorizontalAlign.Center;
 grid.HeaderStyle.BackColor = corHtml("#5D7B9D");
 grid.HeaderStyle.Font.Bold = true;
 grid.HeaderStyle.ForeColor = corHtml("#FFFFFF");
 grid.AlternatingRowStyle.BackColor = corHtml("#FFFFFF");
 grid.AlternatingRowStyle.ForeColor = corHtml("#284775");
 grid.ForeColor = corHtml("#333333");
 grid.CellPadding = 4;

 //define configurações padrões
 grid.AllowPaging = true;
 grid.AllowSorting = true;
 grid.AutoGenerateColumns = false;
 grid.GridLines = GridLines.None;
 grid.PageSize = 20;
 grid.EmptyDataText = " ";
 grid.EnableSortingAndPagingCallbacks = true;
	}

e a função de cor:

public Color corHtml(string cor)
{

 Color corcolor = ColorTranslator.FromHtml(cor);
 return corcolor;
	}