Loop through CheckBoxList Items and save Selected Items in array in ASP.Net

below is the code I have but I want to change the ddl.Deal(dropdownlist) to cbl.Deal(checkboxlist).. How can I loop throught each items if checked. and if all items are checked. to filter my data and show in gridview..

protected void btn_Click(object sender, EventArgs e)
    {
        myAPI.myWeb myAPI = new myAPI.myWeb();
        myAPI.SearchParameters sSearchParameters = new myAPI.SearchParameters();
        DataSet ds = new DataSet();
        DataTable dtFilt= new DataTable();
        DataSet dsFilt = new DataSet();
        DateTime dtmStartDate;
        DateTime dtmEndDate;
    
        
        dtmStartDate = Convert.ToDateTime(txtStartDate.Text);
        dtmEndDate = Convert.ToDateTime(txtEndDate.Text);
	//using dropdownlist but I want to change it to cblDeal (checkboxlist)
        intDeal = Convert.ToInt32(ddlDeal.SelectedValue);
        int[] intDealID = new int[] { intDeal };
        
        SearchParameters.DealID = intDealerID;
        SearchParameters.StartDate = dtmStartDate;
        SearchParameters.EndDate = dtmEndDate;
	//shows gridview with chosen columns to view
        ds = myAPI.Order(SearchParameters);
        dtFiltered.Columns.Add("O ID", typeof(string));
        dtFiltered.Columns.Add("P ID", typeof(string));
        dtFiltered.Columns.Add("C", typeof(string));
        dtFiltered.Columns.Add("F", typeof(string));
        dtFiltered.Columns.Add("D", typeof(string));
        dtFiltered.Columns.Add("S", typeof(string));
        foreach (DataRow row in ds.Tables[0].Rows)
        {
            DataRow newRow = dtFiltered.NewRow();
            newRow["O ID"] = row["OID"].ToString();
            newRow["P ID"] = row["PID"].ToString();
            newRow["C"] = row["C"].ToString();
            newRow["F"] = row["F"].ToString();
            newRow["D"] = row["DCID"].ToString();
            newRow["S"] = row["S"].ToString();
            dtFiltered.Rows.Add(newRow);
        }
        dsFiltered.Tables.Add(dtFilt);
        GridView1.DataSource = dsFilt;
        GridView1.DataBind();
    }