Invalid CurrentPageIndex value. It must be >= 0 and < the PageCount

protected void DataGrid1_PageIndexChanged(Object sender, DataGridPageChangedEventArgs e)
    {

        DataGrid1.CurrentPageIndex = e.NewPageIndex;
        DataGrid1.DataSource = Session["data"] as DataTable;
        DataGrid1.DataBind();
    }
    private void BindGrid()
    {
        DataTable data = storedProcedureManager.sp_inactiveFiles(
                providerID,
                 days, CaseTypeID, CollectorID, user.UserRegID);
        lblMsg.Text = data.Rows.Count + " Record's Found.";
        log.Info(lblMsg.Text);
        Session["data"] = data;
        DataGrid1.DataSource = data;
        DataGrid1.DataBind();

        log.Info("Report Displayed.");

    }
if (!IsPostBack)
       {

           BindGrid();
       }