error - Cannot find table 0

//Data Access code
 
public DataTable getTable(string strQry)
    {
        SqlDataAdapter sqlAdp = new SqlDataAdapter(strQry, strSqlConn);
        try
        {
            strSqlConn.Open();
            DataSet ds = new DataSet();
            sqlAdp.Fill(ds, "Temp");
            return ds.Tables[0];//This is where am getting error
        }
        catch (SqlException ex)
        {
            throw ex;
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            sqlAdp.Dispose();
            sqlAdp = null;
            strSqlConn.Close();
        
        }
 
 
    }
 
//PracticeGridview.cs code
 
public partial class PracticeGridview : System.Web.UI.Page
{
    DataAccess da = new DataAccess();
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            BindGrid();
        }
 
    }
 
    private void BindGrid()
    {
 
        StringBuilder sb = new StringBuilder();
        sb.Append("Select AppID,Application from Approval");
        DataTable dt = new DataTable();
        dt = da.getTable(sb.ToString());
        GridView1.DataSource = dt;
        GridView1.DataBind();
 
    }
 
    protected void Button1_Click1(object sender, EventArgs e)
    {
        for (int i = 0; i < GridView1.Rows.Count; i++)
        {
            int AppID = (int)GridView1.DataKeys[i][0];
            CheckBox cb = (CheckBox)GridView1.Rows[i].FindControl("chkSelect");
 
            if (cb.Checked)
            {
 
                StringBuilder sb = new StringBuilder();
                // sb.Append(GridView1.Rows[i].Cells[1].ToString());
 
                sb.Append("UPDATE Approval SET Approved='true' WHERE AppID=@AppID  ");
                sb.Replace("@AppID", AppID.ToString());
                da.getTable(sb.ToString());
                BindGrid();
            }
        }
    }
}