Gridview paging problem?

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ASP.NET

I used gridview paging and fill from database

each page has 10 data

for ex 1 2 3 each page 10 data there is no problem

1 and 2 has 10 data 3 third page 3 data
I click 3 third page and 2 second page so before

this error gives me

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

so each page has 10 data there is no problem but if last page less then 10 data click last page and click before page this error gives me

my code this:

MySqlConnection conn = new MySqlConnection(connect.connStr);
                    conn.Open();
                    string sql = "select * from xxx where yyy='" + zz+ "'";
                    MySqlCommand cmd = new MySqlCommand(sql, conn);
                    MySqlDataAdapter Adapter = new MySqlDataAdapter(cmd);
                    DataTable daset = new DataTable();
                    Adapter.Fill(daset);
                    GridView1.DataSource = daset;
                    GridView1.DataBind();

                    Cache["xxx"]= daset;

                    conn.Close(); 

protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
       {

           GridView1.PageIndex = e.NewPageIndex;
           gridbinding();
       }

       private void gridbinding()
       {
           GridView1.DataSource = (DataTable) Cache["xxx"];
           GridView1.DataBind();

       }