General practices (tomAYto tomAHto)...

I hate repeating code and sometimes generics can make things a bit easier. One of the things that needs to be done a lot with Drop-down lists is adding a "Please Select" as the first option, but I don't particularly like doing that in the data layer (stored procedure, etc.). I like to add that to the list, but why repeat the same code for every Drop-down list if there are several on the page? Here is one way I like to take care of that:

Here are the supporting Classes:

  01:  #region Supporting Classes

  02:  public interface IReportObject {

  03:      int ID { get; set; }

  04:      string Name { get; set; }

  05:  }

  06:  public class CSP : IReportObject {

  07:      public int ID { get; set; }

  08:      public string Name { get; set; }

  09:  }

  10:  public class Base : IReportObject {

  11:      public int ID { get; set; }

  12:      public string Name { get; set; }

  13:  }

  14:  public class Property : IReportObject {

  15:      public int ID { get; set; }

  16:      public string Name { get; set; }

  17:  }

  18:  #endregion

Here is the method that all my Drop-down list binders will call. Notice the "new()" constraint, which is needed in order to instantiate a generic. Notice also that I'm going ahead here and changing the text based on whether or not the list is empty. It wouldn't be very helpful to have an empty Drop-down list with just a "Please Select" option and nothing else. What's not shown here is that in the presentation layer, if there are no options to select in any given Drop-down list, the control is disabled as well.

  01:  public static void InsertBefore<T>(List<T> list)

  02:    where T : IReportObject, new() {

  03:      list.Insert(0, new T { ID = 0, Name = ((list.Count() > 0) ? 

  04:         "-- Please Select --" : 

  05:         "-- No Data Found --") });

  06:  }

And here is one of the methods binding one of my Drop-down lists calling the method...

  01:  public static List<CSP> GetCSPs() {

  02:      var list = new List<CSP>();

  03:      using (SqlDataReader rs = DBAccess.getRS("cspGetMilitaryCSPs")) {

  04:          while (rs.Read()) {

  05:              list.Add(new CSP {

  06:                  ID = DBAccess.ToInt32(rs["CSPID"], 0),

  07:                  Name = DBAccess.ToStringValue(rs["CSPName"], string.Empty)

  08:              });

  09:          }

  10:      }

  11:      InsertBefore<CSP>(list);

  12:      return list;

  13:  }

Alas, here is another way I'm doing basically the same thing using LINQ's Union operator. Doing it this way circumvents having to call the 'InsertBefore' method:

  01:  protected IEnumerable<PatientData> BindPatientData() {

  02:      List<PatientData> opt = new List<PatientData>();

  03:      IOrderedQueryable<PatientData> set = 

  04:          (from p in db.Patients

  05:           select new PatientData {

  06:               PatientID = p.PatientID,

  07:               PatientName = p.FirstName + " " + p.LastName

  08:           }).OrderBy(o => o.PatientName);

  09:      opt.Add(new PatientData {

  10:          PatientID = -1, 

  11:          PatientName = (set.Count() > 0) ?  

  12:          "-- Please Select --" : "-- No Data Found --"

  13:      });

  14:      return opt.Union(set.AsEnumerable()); 

  15:  }