Cannot find table 0.

Question

this  is my display function it shows error Cannot find table 0.

 public void display()

    {

       

            DataSet ds = new DataSet();

            ds = DB.ExecuteQuery_SP("displayDetails");

            GridView1.DataSource = ds.Tables[0];

            GridView1.DataBind();

 protected void btnSave_Click(object sender, EventArgs e)

    {

        ThreadStart DisplayThread = new ThreadStart(display);

        Thread t2 = new Thread(DisplayThread);

        t2.Start();

        display();

    

        ThreadStart InsertionThread = new ThreadStart(insertion);

        Thread t1 = new Thread(InsertionThread);

        t1.Priority = ThreadPriority.Highest;

        t1.Start();

        //insertion();

        ThreadStart MailThread = new ThreadStart(Mail);

        Thread t3 = new Thread(MailThread);

        t3.Start();

        //Mail();

        display();

        DataSet ds = new DataSet();

        ds = DB.ExecuteQuery_SP("displayDetails");

        GridView1.DataSource = ds.Tables[0];

        GridView1.DataBind();