Sort group item by attribute

Question

I have a repository method which retrieve a list of items, for example:

StaffID: 250026965
Name: Abbasov Islam
FreeTextName: NULL

StaffID: NULL
Name: NULL
FreeTextName: Antonio Puccio

StaffID: 358
Name: Prosinecki Robert
FreeTextName: NULL

I have to sort this list in this manner:

First the items with StaffID > 0 by Name, then the items with StaffID == NULL by FreeTextName.

In the example case:

StaffID: 250026965
Name: Abbasov Islam
FreeTextName: NULL

StaffID: 358
Name: Prosinecki Robert
FreeTextName: NULL

StaffID: NULL
Name: NULL
FreeTextName: Antonio Puccio

At the moment I am doing:

var resList = conn.Query<TeamSheetStaffPoco>("[dbo].[TList]", p, commandType: CommandType.StoredProcedure).AsList();
var result = resList.Where(x => x.StaffID> 0).OrderBy(y => y.Name).ToList();
result.AddRange(resList.Where(x => x.StaffID== null).OrderBy(y => y.FreeTextName).ToList());

It works, but I am not sure if exist a more concise and elegant mode to to do the same thing.

Answer 1

Use a custom IComparer<T> to sort the the items.

class TeamSheetStaffPocoComparer : IComparer<TeamSheetStaffPoco> {

    public int Compare(TeamSheetStaffPoco a, TeamSheetStaffPoco b) {

        if (a.StaffID == null && b.StaffId == null)
        {
            return a.FreeTextName.CompareTo(b.FreeTextName);
        }

        if (a.StaffID > 0 && b.StaffID > 0) 
        {
            return a.Name.CompareTo(b.Name);
        }

        return a.StaffID > 0 ? 1 : -1;
    }

 }

Then you can simplify the last two lines to

var result = resList.OrderBy(x => x, new TeamSheetStaffPocoComparer()).ToList();

Also, you can now reuse the comparison class elsewhere too if you wish.