.NET Development Foundation/Using generic collections

System types and collections: Using generic collections Using generic collections Exam objective: Improve type safety and application performance in a .NET Framework application by using generic collections. (Refer System.Collections.Generic namespace MSDN ) Collection.Generic interfaces Generic IComparable interface - MSDN Note that IComparable<T> is a member of the System namespace. You use this interface when you create a class and you want it to be used with generic types that support ordering (ex. SortedList<T> or List<T>.Sort()) without having to specify a comparer object. The only method of IComparable<T> is CompareTo<T>(T other). There is an example on MSDN. The following example implements IComparable<T> for a custom made Point class. The example uses a List<T> instead of a SortedList<T> or OrderedDictionnary<T> because the comparaison is done based on the distance of the points from the origin which can give the same value for many points. Simple use IComparable<T> (C#) Simple use IComparable<T> (C#) using System; using System.Collections.Generic; using System.Text; namespace GenericsLab05 { class Program { static void Main(string[] args) { List<Point> lst = new List<Point>(); lst.Add(new Point(-2, -2)); lst.Add(new Point(1, 1)); lst.Add(new Point(2, 2)); // Sort uses IComparable of Point lst.Sort(); foreach (Point pt in lst) { Console.WriteLine(pt.ToString()); } // Wait to finish Console.WriteLine("Press ENTER to finish"); Console.ReadLine(); } } // This is out custom version of a point public struct Point : IComparable<Point> { public double x; public double y; public Point(double px, double py) { x = px; y = py; } // Comparaison done based on distance from origin public int CompareTo(Point other) { return Math.Sqrt(Math.Pow(x, 2) + Math.Pow(y, 2)).CompareTo (Math.Sqrt(Math.Pow(other.x, 2) + Math.Pow(other.y, 2))); } public override string ToString() { return "(" + x.ToString() + "," + y.ToString() + ")"; } } } Generic ICollection interface and Generic IList interface Generic ICollection interface - MSDN Generic IList interface - MSDN Generic IComparer interface and Generic IEqualityComparer interface Generic IComparer interface - MSDN Generic IEqualityComparer interface - MSDN Generic IDictionary interface - MSDN Generic IEnumerable interface and Generic IEnumerator interface Generic IEnumerable interface - MSDN see also ONDotnet Generic IEnumerator interface - MSDN IHashCodeProvider interface - MSDN - Interface is now obsolete (as of .NET 2.0) Generic Dictionary Generic Dictionary class and Generic Dictionary.Enumerator structure Generic Dictionary class - MSDN Generic Dictionary.Enumerator structure - MSDN Generic Dictionary.KeyCollection class and Dictionary.KeyCollection.Enumerator structure Generic Dictionary.KeyCollection class - MSDN Dictionary.KeyCollection.Enumerator structure - MSDN Generic Dictionary.ValueCollection class and Dictionary.ValueCollection.Enumerator structure Generic Dictionary.ValueCollection class - MSDN Dictionary.ValueCollection.Enumerator structure - MSDN Generic Comparer class and Generic EqualityComparer class Generic Comparer class - MSDN The Comparer<T> class serves as a base class to easily implement the IComparer<T> interface. The example is the same then for the IComparable<T> except that now a Comparer<T> derived object is given to the List<T>.Sort() method instead of implementing the IComparable<T> interface on Point. This way of preceding has 2 advantages: It can be used even if you dont have access to the source code of Point You can have more than one Comparer derived class for the same Point class Custom Comparer<T> (C#) Custom Comparer<T> (C#) using System; using System.Collections.Generic; using System.Text; namespace GenericsLab06 { class Program { static void Main(string[] args) { List<Point> lst = new List<Point>(); lst.Add(new Point(-2, -2)); lst.Add(new Point(1, 1)); lst.Add(new Point(2, 2)); // Sort uses IComparable of Point lst.Sort(new DistanceComparer()); foreach (Point pt in lst) { Console.WriteLine(pt.ToString()); } // Wait to finish Console.WriteLine("Press ENTER to finish"); Console.ReadLine(); } } // This is out custom version of a point public struct Point { public double x; public double y; public Point(double px, double py) { x = px; y = py; } public override string ToString() { return "(" + x.ToString() + "," + y.ToString() + ")"; } } // Derive from base comparer class to implement IComparer<T> public class DistanceComparer : Comparer<Point> { public override int Compare(Point p1, Point p2) { return Math.Sqrt(Math.Pow(p1.x, 2) + Math.Pow(p1.y, 2)).CompareTo (Math.Sqrt(Math.Pow(p2.x, 2) + Math.Pow(p2.y, 2))); } } } Generic EqualityComparer class - MSDN Generic KeyValuePair structure see MSDN Generic List class, Generic List.Enumerator structure, and Generic SortedList class Generic List class - MSDN A generic list class instance is simply declared using the List<T> syntax where T is the specific type. Generic List.Enumerator structure - MSDN Generic SortedList class - MSDN Generic Queue class and Generic Queue.Enumerator structure Generic Queue class - MSDN Generic Queue.Enumerator structure - MSDN Generic SortedDictionary class See MSDN For differences between SortedList and SortedDictionary are explained see MSDN Generic LinkedList A Generic Linked List represents a doubly linked list and is a general-purpose linked list. It supports enumerators and implements the ICollection interface, consistent with other classes in the .NET Framework. Generic LinkedList class - MSDN Generic LinkedList.Enumerator structure - MSDN Generic LinkedListNode class - MSDN Generic Stack class and Generic Stack.Enumerator structure Generic Stack class - MSDN Generic Stack.Enumerator structure - MSDN