C#集合示例

using System;
using System.Collections.Generic;
using System.Text;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a new dictionary of strings, with string keys.
            //
            Dictionary<string, string> openWith =
                new Dictionary<string, string>();
            // Add some elements to the dictionary. There are no 
            // duplicate keys, but some of the values are duplicates.
            openWith.Add("txt", "notepad.exe");
            openWith.Add("bmp", "paint.exe");
            openWith.Add("dib", "paint.exe");
            openWith.Add("rtf", "wordpad.exe");
            // The Add method throws an exception if the new key is 
            // already in the dictionary.
            try
            {
                openWith.Add("txt", "winword.exe");
            }
            catch (ArgumentException)
            {
                Console.WriteLine("An element with Key = \"txt\" already exists.");
            }
            // The Item property is another name for the indexer, so you 
            // can omit its name when accessing elements. 
            Console.WriteLine("For key = \"rtf\", value = {0}.",
                openWith["rtf"]);
            // The indexer can be used to change the value associated
            // with a key.
            openWith["rtf"] = "winword.exe";
            Console.WriteLine("For key = \"rtf\", value = {0}.",
                openWith["rtf"]);
            // If a key does not exist, setting the indexer for that key
            // adds a new key/value pair.
            openWith["doc"] = "winword.exe";
            // The indexer throws an exception if the requested key is
            // not in the dictionary.
            try
            {
                Console.WriteLine("For key = \"tif\", value = {0}.",
                    openWith["tif"]);
            }
            catch (KeyNotFoundException)
            {
                Console.WriteLine("Key = \"tif\" is not found.");
            }
            // When a program often has to try keys that turn out not to
            // be in the dictionary, TryGetValue can be a more efficient 
            // way to retrieve values.
            string value = "";
            if (openWith.TryGetValue("tif", out value))
            {
                Console.WriteLine("For key = \"tif\", value = {0}.", value);
            }
            else
            {
                Console.WriteLine("Key = \"tif\" is not found.");
            }
            // ContainsKey can be used to test keys before inserting 
            // them.
            if (!openWith.ContainsKey("ht"))
            {
                openWith.Add("ht", "hypertrm.exe");
                Console.WriteLine("Value added for key = \"ht\": {0}",
                    openWith["ht"]);
            }
            // When you use foreach to enumerate dictionary elements,
            // the elements are retrieved as KeyValuePair objects.
            Console.WriteLine();
            foreach (KeyValuePair<string, string> kvp in openWith)
            {
                Console.WriteLine("Key = {0}, Value = {1}",
                    kvp.Key, kvp.Value);
            }
            // To get the values alone, use the Values property.
            Dictionary<string, string>.ValueCollection valueColl =
                openWith.Values;
            // The elements of the ValueCollection are strongly typed
            // with the type that was specified for dictionary values.
            Console.WriteLine();
            foreach (string s in valueColl)
            {
                Console.WriteLine("Value = {0}", s);
            }
            // To get the keys alone, use the Keys property.
            Dictionary<string, string>.KeyCollection keyColl =
                openWith.Keys;
            // The elements of the KeyCollection are strongly typed
            // with the type that was specified for dictionary keys.
            Console.WriteLine();
            foreach (string s in keyColl)
            {
                Console.WriteLine("Key = {0}", s);
            }
            // Use the Remove method to remove a key/value pair.
            Console.WriteLine("\nRemove(\"doc\")");
            openWith.Remove("doc");
            if (!openWith.ContainsKey("doc"))
            {
                Console.WriteLine("Key \"doc\" is not found.");
            }
            Console.ReadKey();
        }
    }
}