IDictionary数据字典使用讲解
接口描述
Represents a nongeneric collection of key/value pairs.[代表一个非泛型的键/值对的集合]。在System.Collections.Generic包下面。所在程序集为mscorlib.dll中。
语法
public Interface IDictionary<TKey,TValue>
:ICollection<KeyValuePair<TKey,TValue>>,IEnumerable<KeyValuePair<TKey,TValue>>,IEnumberable
备注 IDictionary<TKey, TValue> 接口是键/值对的泛型集合的基接口。每个元素都是一个存储在 KeyValuePair<TKey, TValue> 对象中的键/值对。每一对都必须有唯一的键。 实现在是否允许 key 为 null 方面有所不同。 此值可以为 null，并且不必是唯一的。 IDictionary<TKey, TValue> 接口允许对所包含的键和值进行枚举，但这并不意味着任何特定的排序顺序。C# 语言中的 foreach 语句（在 Visual Basic 中为 For Each，在 C++ 中为 for each）需要集合中每个元素的类型。 由于 IDictionary<TKey, TValue> 的每个元素都是一个键/值对，因此元素类型既不是键的类型，也不是值的类型。 而是 KeyValuePair<TKey, TValue> 类型。
代码案例如下:
foreach (KeyValuePair<int, string> kvp in myDictionary)
{
Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}
注：foreach 语句是对枚举数的包装，它只允许从集合中读取，不允许写入集合。
方法列表:
| 方法名 | 方法描述 |
| Add(T) |
将某项添加到 ICollection<T> 中。 （继承自 ICollection<T>。） |
| Add(TKey,TValue) | 在 IDictionary<TKey, TValue> 中添加一个带有所提供的键和值的元素。 |
| Clear() |
清空ICollection<T>中的所有元素。 |
| Contains | 确认ICollection<T>集合中是否有特定的值 |
| ContainsKey |
确认IDictionary<TKey, TValue>集合中是否包含指定键元素。 |
| CopyTo | 从特定的 Array 索引开始，将 ICollection<T> 的元素复制到一个 Array 中。 （继承自 ICollection<T>。） |
| GeEnumurator |
返回一个循环访问集合的枚举器。 （继承自 IEnumerable<T>。） |
| Remove(T) |
移除指定元素 |
| Remove(TKey) | 移除指定键的元素 |
| TryGetValue | 获得与指定键关联的元素值 |
注:扩展方法可到官方MSDN查看:http://msdn.microsoft.com/zh-cn/library/8hyehyw5(v=vs.110).aspx
// Create a new dictionary of strings, with string keys,
// and access it through the IDictionary generic interface.
IDictionary<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.
ICollection<string> icoll = 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 icoll )
{
Console.WriteLine("Value = {0}", s);
}
// To get the keys alone, use the Keys property.
icoll = openWith.Keys;
// The elements of the ValueCollection are strongly typed
// with the type that was specified for dictionary values.
Console.WriteLine();
foreach( string s in icoll )
{
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.ReadLine();