Code
//添加這個引用
using System.Data.SqlClient;

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        BindData();
    }
}
private void BindData()
{
    if (Cache["Cache"] == null)
    {
        SqlConnection con = new SqlConnection("Data Source=
        .\\SQLEXPRESS;AttachDbFilename=|DataDirectory|NORTHWND.MDF;
        Integrated Security=True;User Instance=True");
        SqlDataAdapter ad = new SqlDataAdapter("SELECT * FROM Categories",
         con);
        DataSet ds = new DataSet();
        ad.Fill(ds);
        Cache.Insert("Cache", ds, null, DateTime.Now.AddMinutes(2),
               TimeSpan.Zero);
        GridView1.DataSource = ds;
    }
    else
        GridView1.DataSource = (DataSet)Cache["Cache"];
    GridView1.DataBind();
}

Code
Cache.Insert("Cache", ds, null, DateTime.Now.AddMinutes(2), TimeSpan.Zero);