C# 411 » Collections

Sort C# Array in Descending/Reverse Order

timm — Thu, 14 Aug 2008 14:44:57 +0000

How do you sort a C# array in descending or reverse order? A simple way is to sort the array in ascending order, then reverse it: int[] array = new int[] { 3, 1, 4, 5, 2 }; Array.Sort<int>( array ); Array.Reverse( array ); Of course, this is not efficient for large arrays. A better approach is to create a [...] Related posts:

C# Empty Enumerator

timm — Tue, 10 Jun 2008 13:19:20 +0000

This article provides C# code for an empty enumerator. This generic class can be used to simulate enumeration over an empty collection of any type of objects. Here is the code: using System; using System.Collections; using System.Collections.Generic; public class EmptyEnumerator<T> : IEnumerator<T> { public T Current { [...] Related posts:

Multiple Generic IEnumerable

timm — Wed, 28 May 2008 19:28:04 +0000

It's possible to provide multiple generic enumerators for a single class. The trick is that clients must specify which enumerator to use. For example, here is a "MyNumbers" class with multiple generic enumerators (in this case, for custom class "MyInt" and integer): public class MyNumbers : IEnumerable<MyInt>, IEnumerable<int> To enumerate through the class, you must [...] Related posts:

Enumerate Collections without Exceptions

timm — Tue, 06 May 2008 13:35:25 +0000

It's important to note that an enumerator does not have exclusive, thread-safe access to its collection. Even when a collection is synchronized, other threads can still modify the collection. Therefore, a collection's contents can change while enumerating through it, which will cause the enumerator to throw an exception. So there are three key ways to [...] Related posts:

Grow Your Own SyncRoot

timm — Tue, 29 Apr 2008 16:18:22 +0000

Multi-threaded code is challenging to get right and even harder to debug once it's gone wrong. This is especially true when attempting to collect data from multiple threads. To make this easier, many .NET collection classes include the SyncRoot property to maintain proper synchronization with other threads that might be simultaneously modifying the [...] Related posts:

Reverse an Array

timm — Tue, 18 Mar 2008 15:49:00 +0000

It's easy to reverse the contents of an array using C# generics: static T[] ReverseArray<T>( T[] array ) { T[] newArray = null; int count = array == null ? 0 : array.Length; if (count > 0) { [...] Related posts:

Convert Generic ICollection

timm — Thu, 13 Mar 2008 14:21:44 +0000

As discussed in a previous article, Generics provides the ability to create strongly-typed collections in C#. Unfortunately, C# currently does not support generics variance, which would allow inheritance of generic types. Generics Variance: Not Allowed For example, imagine two classes: public class A {} public class B : A {} Now imagine two generic List collections and ICollection interfaces: List<A> [...] Related posts:

KeyedCollection: Dictionary for Values with Embedded Keys

timm — Mon, 04 Feb 2008 16:24:19 +0000

If you need a collection of objects accessed by a key, and the key is one of the object's properties, then you should use the KeyedCollection class instead of Dictionary. For example, you would use a KeyedCollection to store Employee objects accessed by the employee's ID property. The KeyedCollection class is a hybrid between an [...] Related posts:

Convert Between Generic IEnumerable

timm — Thu, 20 Sep 2007 21:43:49 +0000

Generics in .NET 2.0 provides the ability to create strongly-typed collections in C#. Unfortunately, C# currently does not support generics variance, which would allow inheritance of generic types. For example, consider a list of strings and a list of objects: List<string> strings = new List<string>(); strings.Add( "hello" ); strings.Add( "goodbye" ); List<object> objects = new List<object>(); objects.AddRange( strings ); The final [...] Related posts: