C# - bool Sort Examples (True to False)

First example. One use for sorting bools is reordering a List of objects. Sometimes, you need to mark some elements in the List as "bad," pushing them to the bottom of the List.

Tip Bools have a default of false in a class or struct. With bools, the default Sort method will put false before true.

true, false

Info The example populates a List generic with 5 bool values. It displays the List in that state, and then sorts it with List.Sort method.

Detail The default Sort method orders the bools from False to True. This is just like ordering 0 to 1.

Here The descending keyword in the example uses the LINQ query syntax, which is useful for sorting.

using System; using System.Collections.Generic; using System.Linq; class Program { static void Main() { var items = new List<bool>(); items.Add(true); items.Add(false); items.Add(false); items.Add(false); items.Add(true); foreach (bool value in items) { Console.WriteLine("UNSORTED: {0}", value); } // Sort. items.Sort(); foreach (bool value in items) { Console.WriteLine("SORTED: {0}", value); } // Sort descending. var sorted = from item in items orderby item descending select item; foreach (bool value in sorted) { Console.WriteLine("REVERSE SORTED: {0}", value); } } }

UNSORTED: True UNSORTED: False UNSORTED: False UNSORTED: False UNSORTED: True SORTED: False SORTED: False SORTED: False SORTED: True SORTED: True REVERSE SORTED: True REVERSE SORTED: True REVERSE SORTED: False REVERSE SORTED: False REVERSE SORTED: False

Example, bool property. Bool sorting can implement a selection algorithm. Only one element should be chosen, but no elements should be eliminated.

Here We create a List of TestData items. We then sort them with the IsImportant property—important items come before unimportant ones.

Info This approach can improve error handling as it does not eliminate any elements from consideration.

Finally We can exit the foreach-loop with a break or return when we find an item that matches our conditions.

foreach

using System; using System.Collections.Generic; using System.Linq; class TestData { public bool IsImportant { get; set; } public string Data { get; set; } } class Program { static void Main() { // Add data to the list. var items = new List<TestData>(); items.Add(new TestData() { IsImportant = true, Data = "Bird" }); items.Add(new TestData() { IsImportant = false, Data = "Cat" }); items.Add(new TestData() { IsImportant = true, Data = "Human" }); // Sort by bool on class. var sorted = from item in items orderby item.IsImportant descending select item; // Put "important" items first. foreach (var item in sorted) { Console.WriteLine("ITEM: " + item.IsImportant + "; " + item.Data); } } }

ITEM: True; Bird ITEM: True; Human ITEM: False; Cat

A discussion. To filter, you can add a bool property or field to your class, and then as sign that to true or false depending on whether you want to give the item priority.

So Use true to promote the class. Sort the objects with the LINQ query syntax, using the order by descending clause.

orderby

Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.

Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.

This page was last updated on Mar 22, 2023 (edit).

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