array searching

 public void fillgrid()
    {
        bool Mbook = false;
        string[] filld = new string[2];
        string[] oper = new string[2];
        string[] val = new string[2];
        int k = 0;
        bool Mcommon = false;
        string str = "select * from View_avlflat where FLATNO!='999' and  BOOK='" + Mbook + "' and common='" + Mcommon + "' and ";


        if (ddlprojectsite.SelectedIndex != 0)
        {
            filld[k] = "PROJECTCODE";
            oper[k] = "="; ;
            val[k] = "'" + ddlprojectsite.SelectedValue + "'";
            k++;
        }

        if (ddlFlateType.SelectedIndex != 0)
        {
            filld[k] = "flattypeId";
            oper[k] = "="; ;
            val[k] = "'" + ddlFlateType.SelectedValue + "'";
            k++;
        }



        for (int i = 0; i < k; i++)
        {
            str = str + filld[i] + oper[i] + val[i] + " and ";
        }

        //if (str.Substring(str.Length - 4, 4) == "and ")
        //{
        str = str.Substring(0, str.Length - 4);
        //}

        con.Open();
        SqlDataAdapter da = new SqlDataAdapter(str, con);
        DataSet ds = new DataSet();
        da.Fill(ds);
        con.Close();
        gvflateavalable.DataSource = ds;
        gvflateavalable.DataBind();

        if (gvflateavalable.Rows.Count > 0)
        {
            Button3.Visible = true;
            Button4.Visible = true;
        }


        ReportViewer1.LocalReport.DataSources.Clear();
        ReportDataSource reportDSHeader = new ReportDataSource("AvailableFlat_View_avlflat", ds.Tables[0]);
        ReportViewer1.LocalReport.DataSources.Add(reportDSHeader);
        ReportViewer1.LocalReport.Refresh();

    }