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Daniel Martin |

I'm using C# on Framework 3.5. I'm looking to quickly sort a Generic List<T>. For the sake of this example, let's say I have a List of a Person type with a property of lastname. How would I sort this List using a lambda expression?

List<Person> people = PopulateList();
people.OrderBy(???? => ?????)
0

9 Answers

If you mean an in-place sort (i.e. the list is updated):

people.Sort((x, y) => string.Compare(x.LastName, y.LastName));

If you mean a new list:

var newList = people.OrderBy(x=>x.LastName).ToList(); // ToList optional
9

Do you need the list to be sorted in place, or just an ordered sequence of the contents of the list? The latter is easier:

var peopleInOrder = people.OrderBy(person => person.LastName);

To sort in place, you'd need an IComparer<Person> or a Comparison<Person>. For that, you may wish to consider ProjectionComparer in MiscUtil.

(I know I keep bringing MiscUtil up - it just keeps being relevant...)

2

you can use linq :) using :

System.linq;
var newList = people.OrderBy(x=>x.Name).ToList();
people.OrderBy(person => person.lastname).ToList();
3 
private void SortGridGenerico< T >( ref List< T > lista , SortDirection sort , string propriedadeAOrdenar)
{ if (!string.IsNullOrEmpty(propriedadeAOrdenar) && lista != null && lista.Count > 0) { Type t = lista[0].GetType(); if (sort == SortDirection.Ascending) { lista = lista.OrderBy( a => t.InvokeMember( propriedadeAOrdenar , System.Reflection.BindingFlags.GetProperty , null , a , null ) ).ToList(); } else { lista = lista.OrderByDescending( a => t.InvokeMember( propriedadeAOrdenar , System.Reflection.BindingFlags.GetProperty , null , a , null ) ).ToList(); } }
}

for me this useful dummy guide - Sorting in Generic List - worked. it helps you to understand 4 ways(overloads) to do this job with very complete and clear explanations and simple examples

  • List.Sort ()
  • List.Sort (Generic Comparison)
  • List.Sort (Generic IComparer)
  • List.Sort (Int32, Int32, Generic IComparer)
1

You can use this code snippet:

var New1 = EmpList.OrderBy(z => z.Age).ToList();

where New1 is a List<Employee>.

EmpList is variable of a List<Employee>.

z is a variable of Employee type.

1

You can also use

model.People = model.People.OrderBy(x => x.Name).ToList();
1

This is a generic sorter. Called with the switch below.

dvm.PagePermissions is a property on my ViewModel of type List T in this case T is a EF6 model class called page_permission.

dvm.UserNameSortDir is a string property on the viewmodel that holds the next sort direction. The one that is actaully used in the view.

switch (sortColumn)
{ case "user_name": dvm.PagePermissions = Sort(dvm.PagePermissions, p => p.user_name, ref sortDir); dvm.UserNameSortDir = sortDir; break; case "role_name": dvm.PagePermissions = Sort(dvm.PagePermissions, p => p.role_name, ref sortDir); dvm.RoleNameSortDir = sortDir; break; case "page_name": dvm.PagePermissions = Sort(dvm.PagePermissions, p => p.page_name, ref sortDir); dvm.PageNameSortDir = sortDir; break;
}
public List<T> Sort<T,TKey>(List<T> list, Func<T, TKey> sorter, ref string direction) { if (direction == "asc") { list = list.OrderBy(sorter).ToList(); direction = "desc"; } else { list = list.OrderByDescending(sorter).ToList(); direction = "asc"; } return list; }
3

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