how to retrieve data from combobox

QueryRet QR = new QueryRet(); Query = "Select ProjectId from TblProjects where ProjectName = '" + ProjectName.Text.ToString() + "'"; QR.SelectQry(Query).ToString(); Query = "Select Id from TblTeam WHERE FirstName = '" + User.Identity.Name + "'"; DevId = QR.SelectQry(Query).ToString(); Query = "Select * from TblTimeSheets Where WeekStartDate = " + StartDate + " AND ProjectId = '" + ProjectId + "' AND DevId = '" + DevId + "'"; SqlConnection sqlConnection1 = new System.Data.SqlClient.SqlConnection(ConnString.ToString());