18 C# 第十六章 集合的使用
这里主要整理了一些集合使用的例子，便于在工作时查找和使用。
这些段代码主要来自 MSDN。
代码实例： List_Sample
注意其中的 Count 和 Capacity的区别。
Count ：集合中有多少个元素。
MSDN <http://msdn.microsoft.com/en-us/library/xfhwa508.aspx>
注意如果 名称(或键值) 在Dictionary已经存在了，如果在向其添加值会引发异常。可以使用ContainsKey()进行检查。
代码实例： Dictionary_Sample
MSDN <http://msdn.microsoft.com/zh-cn/library/vstudio/f7fta44c.aspx>
代码实例： SortedDictionary_Sample
MSDN <http://msdn.microsoft.com/en-us/library/3278tedw.aspx>
代码实例： Stack_Sample
MSDN <http://msdn.microsoft.com/en-us/library/7977ey2c.aspx>
这些段代码主要来自 MSDN。
List<T>
与数组有相似的属性，但随着元素的增加，其容量也会自动的扩展。当然也可以通过 TrimToSize或 Capacity来缩小其空间。MSDN <http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx>
代码实例： List_Sample
using System;
using System.Collections.Generic;
public class Example
{
public static bool MyFilter(string value)
{
return value.Contains("Fi");
}
public static void Main()
{
List<string> dinosaurs = new List<string>();
Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);
dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Mamenchisaurus");
dinosaurs.Add("Deinonychus");
dinosaurs.Add("Compsognathus");
Console.WriteLine();
foreach (string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);
Console.WriteLine("\nContains(\"Deinonychus\"): {0}",
dinosaurs.Contains("Deinonychus"));
Console.WriteLine("\nInsert(2, \"Compsognathus\")");
dinosaurs.Insert(2, "Compsognathus");
Console.WriteLine();
foreach (string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]);
Console.WriteLine("\nRemove(\"Compsognathus\")");
dinosaurs.Remove("Compsognathus");
Console.WriteLine();
foreach (string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine();
Console.WriteLine("======== Sort the list =======");
dinosaurs.Sort();
foreach (string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine();
Console.WriteLine("======== BinarySearch 方法 =======");
int nSearch = dinosaurs.BinarySearch("Five");
if (nSearch < 0)
{
dinosaurs.Insert(~nSearch, "Five");
}
foreach (string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine();
Console.WriteLine();
Console.WriteLine("======== FindAll 方法 Print the subList =======");
List<string> subList = dinosaurs.FindAll(MyFilter);
foreach (string item in subList)
{
Console.WriteLine(item);
}
Console.WriteLine();
dinosaurs.TrimExcess();
Console.WriteLine("\nTrimExcess()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);
dinosaurs.Clear();
Console.WriteLine("\nClear()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);
Console.ReadKey();
}
}
注意其中的 Count 和 Capacity的区别。
Count ：集合中有多少个元素。
Capacity：集合有多大的空间，就是指当前在不用调用resize的情况下可以容纳元素的最大个数。
BinarySearch：List<T>支持排序，在运行了Sort()方法后，可以使用BinarySearch进行二分查找。BinarySearch很有特点，如果元素没有找到，它会返回一个负整数，对该值进行按位取反(~)， 就会得到"大于被查找元素的下一个元素的位置"， 简单的说就是我们要找的元素可以被顺序插入的地方，这个特点可以让程序轻松的在保持集合排序的状态下，轻松的插入一个元素。执行BinarySearch的前提是一定要执行 Sort()函数。
Dictionary<TKey, TValue>
使用 名称/值 对应的方式来保存数据的。MSDN <http://msdn.microsoft.com/en-us/library/xfhwa508.aspx>
注意如果 名称(或键值) 在Dictionary已经存在了，如果在向其添加值会引发异常。可以使用ContainsKey()进行检查。
代码实例： Dictionary_Sample
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Dictionary_Sample
{
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.");
}
Console.WriteLine("\n");
// 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"]);
Console.WriteLine("\n");
// 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.");
}
Console.WriteLine("\n");
// 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.");
}
Console.WriteLine("\n");
// 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"]);
}
Console.WriteLine("\n");
// 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);
}
Console.WriteLine("\n");
// 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);
}
Console.WriteLine("\n");
// 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);
}
Console.WriteLine("\n");
// 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();
}
}
}
SortedDictionary<TKey, TValue>
与Dictionary的使用基本一致 用名称/值 对应的方式来保存数据的，但它还有个特定，元素是按键值排好序的。MSDN <http://msdn.microsoft.com/zh-cn/library/vstudio/f7fta44c.aspx>
代码实例： SortedDictionary_Sample
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace SortedDictionary_Sample
{
class Program
{
static void Main(string[] args)
{
// Create a new sorted dictionary of strings, with string
// keys.
SortedDictionary<string, string> openWith =
new SortedDictionary<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.
SortedDictionary<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.
SortedDictionary<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();
}
}
}
Stack<T>
后进先出的存储方式MSDN <http://msdn.microsoft.com/en-us/library/3278tedw.aspx>
代码实例： Stack_Sample
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Stack_Sample
{
class Program
{
static void Main(string[] args)
{
Stack<string> numbers = new Stack<string>();
numbers.Push("one");
numbers.Push("two");
numbers.Push("three");
numbers.Push("four");
numbers.Push("five");
// A stack can be enumerated without disturbing its contents.
foreach (string number in numbers)
{
Console.WriteLine(number);
}
Console.WriteLine("\nPopping '{0}'", numbers.Pop());
Console.WriteLine("Peek at next item to destack: {0}", numbers.Peek());
Console.WriteLine("Popping '{0}'", numbers.Pop());
// Create a copy of the stack, using the ToArray method and the
// constructor that accepts an IEnumerable<T>.
Stack<string> stack2 = new Stack<string>(numbers.ToArray());
Console.WriteLine("\nContents of the first copy:");
foreach (string number in stack2)
{
Console.WriteLine(number);
}
// Create an array twice the size of the stack and copy the
// elements of the stack, starting at the middle of the
// array.
string[] array2 = new string[numbers.Count * 2];
numbers.CopyTo(array2, numbers.Count);
// Create a second stack, using the constructor that accepts an
// IEnumerable(Of T).
Stack<string> stack3 = new Stack<string>(array2);
Console.WriteLine("\nContents of the second copy, with duplicates and nulls:");
foreach (string number in stack3)
{
Console.WriteLine(number);
}
Console.WriteLine("\nstack2.Contains(\"four\") = {0}", stack2.Contains("four"));
Console.WriteLine("\nstack2.Clear()");
stack2.Clear();
Console.WriteLine("\nstack2.Count = {0}", stack2.Count);
Console.ReadKey();
}
}
}
Queue<T>
先进先出的存储方式MSDN <http://msdn.microsoft.com/en-us/library/7977ey2c.aspx>
代码实例： Queue_Sample
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Queue_Sample
{
class Program
{
static void Main(string[] args)
{
Queue<string> numbers = new Queue<string>();
numbers.Enqueue("one");
numbers.Enqueue("two");
numbers.Enqueue("three");
numbers.Enqueue("four");
numbers.Enqueue("five");
// A queue can be enumerated without disturbing its contents.
foreach (string number in numbers)
{
Console.WriteLine(number);
}
Console.WriteLine("\nDequeuing '{0}'", numbers.Dequeue());
Console.WriteLine("Peek at next item to dequeue: {0}", numbers.Peek());
Console.WriteLine("Dequeuing '{0}'", numbers.Dequeue());
// Create a copy of the queue, using the ToArray method and the
// constructor that accepts an IEnumerable<T>.
Queue<string> queueCopy = new Queue<string>(numbers.ToArray());
Console.WriteLine("\nContents of the first copy:");
foreach (string number in queueCopy)
{
Console.WriteLine(number);
}
// Create an array twice the size of the queue and copy the
// elements of the queue, starting at the middle of the
// array.
string[] array2 = new string[numbers.Count * 2];
numbers.CopyTo(array2, numbers.Count);
// Create a second queue, using the constructor that accepts an
// IEnumerable(Of T).
Queue<string> queueCopy2 = new Queue<string>(array2);
Console.WriteLine("\nContents of the second copy, with duplicates and nulls:");
foreach (string number in queueCopy2)
{
Console.WriteLine(number);
}
Console.WriteLine("\nqueueCopy.Contains(\"four\") = {0}", queueCopy.Contains("four"));
Console.WriteLine("\nqueueCopy.Clear()");
queueCopy.Clear();
Console.WriteLine("\nqueueCopy.Count = {0}", queueCopy.Count);
Console.ReadKey();
}
}
}
LinkedList<T>
一个链表，支持正向和反向的遍历。
MSDN <http://msdn.microsoft.com/en-us/library/he2s3bh7.aspx>
代码实例： LinkedList_Sample
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LinkedList_Sample
{
class Program
{
static void Main(string[] args)
{
// Create the link list.
string[] words = { "the", "fox", "jumped", "over", "the", "dog" };
LinkedList<string> sentence = new LinkedList<string>(words);
Display(sentence, "The linked list values:");
Console.WriteLine("sentence.Contains(\"jumped\") = {0}", sentence.Contains("jumped"));
// Add the word 'today' to the beginning of the linked list.
sentence.AddFirst("today");
Display(sentence, "Test 1: Add 'today' to beginning of the list:");
// Move the first node to be the last node.
LinkedListNode<string> mark1 = sentence.First;
sentence.RemoveFirst();
sentence.AddLast(mark1);
Display(sentence, "Test 2: Move first node to be last node:");
// Change the last node be 'yesterday'.
sentence.RemoveLast();
sentence.AddLast("yesterday");
Display(sentence, "Test 3: Change the last node to 'yesterday':");
// Move the last node to be the first node.
mark1 = sentence.Last;
sentence.RemoveLast();
sentence.AddFirst(mark1);
Display(sentence, "Test 4: Move last node to be first node:");
// Indicate, by using parentheisis, the last occurence of 'the'.
sentence.RemoveFirst();
LinkedListNode<string> current = sentence.FindLast("the");
IndicateNode(current, "Test 5: Indicate last occurence of 'the':");
// Add 'lazy' and 'old' after 'the' (the LinkedListNode named current).
sentence.AddAfter(current, "old");
sentence.AddAfter(current, "lazy");
IndicateNode(current, "Test 6: Add 'lazy' and 'old' after 'the':");
// Indicate 'fox' node.
current = sentence.Find("fox");
IndicateNode(current, "Test 7: Indicate the 'fox' node:");
// Add 'quick' and 'brown' before 'fox':
sentence.AddBefore(current, "quick");
sentence.AddBefore(current, "brown");
IndicateNode(current, "Test 8: Add 'quick' and 'brown' before 'fox':");
// Keep a reference to the current node, 'fox',
// and to the previous node in the list. Indicate the 'dog' node.
mark1 = current;
LinkedListNode<string> mark2 = current.Previous;
current = sentence.Find("dog");
IndicateNode(current, "Test 9: Indicate the 'dog' node:");
// The AddBefore method throws an InvalidOperationException
// if you try to add a node that already belongs to a list.
Console.WriteLine("Test 10: Throw exception by adding node (fox) already in the list:");
try
{
sentence.AddBefore(current, mark1);
}
catch (InvalidOperationException ex)
{
Console.WriteLine("Exception message: {0}", ex.Message);
}
Console.WriteLine();
// Remove the node referred to by mark1, and then add it
// before the node referred to by current.
// Indicate the node referred to by current.
sentence.Remove(mark1);
sentence.AddBefore(current, mark1);
IndicateNode(current, "Test 11: Move a referenced node (fox) before the current node (dog):");
// Remove the node referred to by current.
sentence.Remove(current);
IndicateNode(current, "Test 12: Remove current node (dog) and attempt to indicate it:");
// Add the node after the node referred to by mark2.
sentence.AddAfter(mark2, current);
IndicateNode(current, "Test 13: Add node removed in test 11 after a referenced node (brown):");
// The Remove method finds and removes the
// first node that that has the specified value.
sentence.Remove("old");
Display(sentence, "Test 14: Remove node that has the value 'old':");
// When the linked list is cast to ICollection(Of String),
// the Add method adds a node to the end of the list.
sentence.RemoveLast();
ICollection<string> icoll = sentence;
icoll.Add("rhinoceros");
Display(sentence, "Test 15: Remove last node, cast to ICollection, and add 'rhinoceros':");
Console.WriteLine("Test 16: Copy the list to an array:");
// Create an array with the same number of
// elements as the inked list.
string[] sArray = new string[sentence.Count];
sentence.CopyTo(sArray, 0);
foreach (string s in sArray)
{
Console.WriteLine(s);
}
// Release all the nodes.
sentence.Clear();
Console.WriteLine();
Console.WriteLine("Test 17: Clear linked list. Contains 'jumped' = {0}",
sentence.Contains("jumped"));
Console.ReadKey();
}
private static void Display(LinkedList<string> words, string test)
{
Console.WriteLine(test);
foreach (string word in words)
{
Console.Write(word + " ");
}
Console.WriteLine();
Console.WriteLine();
}
private static void IndicateNode(LinkedListNode<string> node, string test)
{
Console.WriteLine(test);
if (node.List == null)
{
Console.WriteLine("Node '{0}' is not in the list.\n", node.Value);
return;
}
StringBuilder result = new StringBuilder("(" + node.Value + ")");
LinkedListNode<string> nodeP = node.Previous;
while (nodeP != null)
{
result.Insert(0, nodeP.Value + " ");
nodeP = nodeP.Previous;
}
node = node.Next;
while (node != null)
{
result.Append(" " + node.Value);
node = node.Next;
}
Console.WriteLine(result);
Console.WriteLine();
}
}
}