Dictionary<TKey,TValue> 类
定义
重要
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表示键和值的集合。
generic <typename TKey, typename TValue>
public ref class Dictionary : System::Collections::Generic::ICollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IDictionary<TKey, TValue>, System::Collections::Generic::IEnumerable<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyCollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyDictionary<TKey, TValue>, System::Collections::IDictionarygeneric <typename TKey, typename TValue>
public ref class Dictionary : System::Collections::Generic::ICollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IDictionary<TKey, TValue>, System::Collections::Generic::IEnumerable<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyCollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyDictionary<TKey, TValue>, System::Collections::IDictionary, System::Runtime::Serialization::IDeserializationCallback, System::Runtime::Serialization::ISerializablegeneric <typename TKey, typename TValue>
public ref class Dictionary : System::Collections::Generic::ICollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IDictionary<TKey, TValue>, System::Collections::Generic::IEnumerable<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::IDictionary, System::Runtime::Serialization::IDeserializationCallback, System::Runtime::Serialization::ISerializablepublic class Dictionary<TKey,TValue> : System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IDictionary<TKey,TValue>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyDictionary<TKey,TValue>, System.Collections.IDictionarypublic class Dictionary<TKey,TValue> : System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IDictionary<TKey,TValue>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyDictionary<TKey,TValue>, System.Collections.IDictionary, System.Runtime.Serialization.IDeserializationCallback, System.Runtime.Serialization.ISerializable[System.Runtime.InteropServices.ComVisible(false)]
[System.Serializable]
public class Dictionary<TKey,TValue> : System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IDictionary<TKey,TValue>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.IDictionary, System.Runtime.Serialization.IDeserializationCallback, System.Runtime.Serialization.ISerializable[System.Runtime.InteropServices.ComVisible(false)]
[System.Serializable]
public class Dictionary<TKey,TValue> : System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IDictionary<TKey,TValue>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyDictionary<TKey,TValue>, System.Collections.IDictionary, System.Runtime.Serialization.IDeserializationCallback, System.Runtime.Serialization.ISerializabletype Dictionary<'Key, 'Value> = class
interface ICollection<KeyValuePair<'Key, 'Value>>
interface seq<KeyValuePair<'Key, 'Value>>
interface IEnumerable
interface IDictionary<'Key, 'Value>
interface IReadOnlyCollection<KeyValuePair<'Key, 'Value>>
interface IReadOnlyDictionary<'Key, 'Value>
interface ICollection
interface IDictionarytype Dictionary<'Key, 'Value> = class
interface ICollection<KeyValuePair<'Key, 'Value>>
interface seq<KeyValuePair<'Key, 'Value>>
interface IEnumerable
interface IDictionary<'Key, 'Value>
interface IReadOnlyCollection<KeyValuePair<'Key, 'Value>>
interface IReadOnlyDictionary<'Key, 'Value>
interface ICollection
interface IDictionary
interface IDeserializationCallback
interface ISerializable[<System.Runtime.InteropServices.ComVisible(false)>]
[<System.Serializable>]
type Dictionary<'Key, 'Value> = class
interface IDictionary<'Key, 'Value>
interface ICollection<KeyValuePair<'Key, 'Value>>
interface seq<KeyValuePair<'Key, 'Value>>
interface IDictionary
interface ICollection
interface IEnumerable
interface ISerializable
interface IDeserializationCallback[<System.Runtime.InteropServices.ComVisible(false)>]
[<System.Serializable>]
type Dictionary<'Key, 'Value> = class
interface IDictionary<'Key, 'Value>
interface ICollection<KeyValuePair<'Key, 'Value>>
interface IDictionary
interface ICollection
interface IReadOnlyDictionary<'Key, 'Value>
interface IReadOnlyCollection<KeyValuePair<'Key, 'Value>>
interface seq<KeyValuePair<'Key, 'Value>>
interface IEnumerable
interface ISerializable
interface IDeserializationCallback[<System.Runtime.InteropServices.ComVisible(false)>]
[<System.Serializable>]
type Dictionary<'Key, 'Value> = class
interface IDictionary<'Key, 'Value>
interface ICollection<KeyValuePair<'Key, 'Value>>
interface seq<KeyValuePair<'Key, 'Value>>
interface IEnumerable
interface IDictionary
interface ICollection
interface IReadOnlyDictionary<'Key, 'Value>
interface IReadOnlyCollection<KeyValuePair<'Key, 'Value>>
interface ISerializable
interface IDeserializationCallbacktype Dictionary<'Key, 'Value> = class
interface IDictionary<'Key, 'Value>
interface ICollection<KeyValuePair<'Key, 'Value>>
interface IReadOnlyDictionary<'Key, 'Value>
interface IReadOnlyCollection<KeyValuePair<'Key, 'Value>>
interface seq<KeyValuePair<'Key, 'Value>>
interface IDictionary
interface ICollection
interface IEnumerablePublic Class Dictionary(Of TKey, TValue)
Implements ICollection(Of KeyValuePair(Of TKey, TValue)), IDictionary, IDictionary(Of TKey, TValue), IEnumerable(Of KeyValuePair(Of TKey, TValue)), IReadOnlyCollection(Of KeyValuePair(Of TKey, TValue)), IReadOnlyDictionary(Of TKey, TValue)Public Class Dictionary(Of TKey, TValue)
Implements ICollection(Of KeyValuePair(Of TKey, TValue)), IDeserializationCallback, IDictionary, IDictionary(Of TKey, TValue), IEnumerable(Of KeyValuePair(Of TKey, TValue)), IReadOnlyCollection(Of KeyValuePair(Of TKey, TValue)), IReadOnlyDictionary(Of TKey, TValue), ISerializablePublic Class Dictionary(Of TKey, TValue)
Implements ICollection(Of KeyValuePair(Of TKey, TValue)), IDeserializationCallback, IDictionary, IDictionary(Of TKey, TValue), IEnumerable(Of KeyValuePair(Of TKey, TValue)), ISerializable类型参数
- TKey
字典中键的类型。
- TValue
字典中值的类型。
- 继承
-
Dictionary<TKey,TValue>
- 派生
- 属性
- 实现
-
ICollection<KeyValuePair<TKey,TValue>> IDictionary<TKey,TValue> IEnumerable<KeyValuePair<TKey,TValue>> IEnumerable<T> IReadOnlyCollection<KeyValuePair<TKey,TValue>> IReadOnlyDictionary<TKey,TValue> ICollection IDictionary IEnumerable IDeserializationCallback ISerializable
示例
下面的代码示例使用字符串键创建一个空的字符串 Dictionary<TKey,TValue>，并使用 Add 方法添加一些元素。 该示例演示 Add 方法在尝试添加重复键时引发 ArgumentException。
该示例使用 Item[] 属性（C# 中的索引器）检索值，演示请求的键不存在时引发 KeyNotFoundException，并显示可以替换与键关联的值。
该示例演示如何将 TryGetValue 方法用作检索值的更有效方法（如果程序经常必须尝试不在字典中的键值），并演示如何使用 ContainsKey 方法测试键是否存在，然后再调用 Add 方法。
该示例演示如何枚举字典中的键和值，以及如何使用 Keys 属性和 Values 属性单独枚举键和值。
最后，该示例演示 Remove 方法。
using namespace System;
using namespace System::Collections::Generic;
public ref class Example
{
public:
static void Main()
{
// Create a new dictionary of strings, with string keys.
//
Dictionary<String^, String^>^ openWith =
gcnew 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", 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();
for each( 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();
for each( 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();
for each( 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.");
}
}
};
int main()
{
Example::Main();
}
/* This code example produces the following output:
An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe
Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = winword.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe
Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = winword.exe
Value = hypertrm.exe
Key = txt
Key = bmp
Key = dib
Key = rtf
Key = doc
Key = ht
Remove("doc")
Key "doc" is not found.
*/
// 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.");
}
/* This code example produces the following output:
An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe
Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = winword.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe
Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = winword.exe
Value = hypertrm.exe
Key = txt
Key = bmp
Key = dib
Key = rtf
Key = doc
Key = ht
Remove("doc")
Key "doc" is not found.
*/
// Create a new dictionary of strings, with string keys.
let openWith = 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")
with :? ArgumentException ->
printfn "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.
printfn $"""For key = "rtf", value = {openWith["rtf"]}"""
// The indexer can be used to change the value associated
// with a key.
openWith["rtf"] <- "winword.exe"
printfn $"""For key = "rtf", value = {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
printfn $"""For key = "tif", value = {openWith["tif"]}"""
with :? KeyNotFoundException ->
printfn "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.
match openWith.TryGetValue "tif" with
| true, value -> printfn $"For key = \"tif\", value = {value}."
| _ -> printfn "Key = \"tif\" is not found."
// ContainsKey can be used to test keys before inserting
// them.
if openWith.ContainsKey "ht" |> not then
openWith.Add("ht", "hypertrm.exe")
printfn $"""Value added for key = "ht": {openWith["ht"]}"""
// When you use foreach to enumerate dictionary elements,
// the elements are retrieved as KeyValuePair objects.
printfn ""
for kvp in openWith do
printfn $"Key = {kvp.Key}, Value = {kvp.Value}"
// To get the values alone, use the Values property.
let valueColl = openWith.Values
// The elements of the ValueCollection are strongly typed
// with the type that was specified for dictionary values.
printfn ""
for s in valueColl do
printfn $"Value = {s}"
// To get the keys alone, use the Keys property.
let keyColl = openWith.Keys
// The elements of the KeyCollection are strongly typed
// with the type that was specified for dictionary keys.
printfn ""
for s in keyColl do
printfn $"Key = {s}"
// Use the Remove method to remove a key/value pair.
printfn "\nRemove(\"doc\")"
openWith.Remove "doc" |> ignore
if openWith.ContainsKey "doc" |> not then
printfn "Key \"doc\" is not found."
// This code example produces the following output:
// An element with Key = "txt" already exists.
// For key = "rtf", value = wordpad.exe.
// For key = "rtf", value = winword.exe.
// Key = "tif" is not found.
// Key = "tif" is not found.
// Value added for key = "ht": hypertrm.exe
//
// Key = txt, Value = notepad.exe
// Key = bmp, Value = paint.exe
// Key = dib, Value = paint.exe
// Key = rtf, Value = winword.exe
// Key = doc, Value = winword.exe
// Key = ht, Value = hypertrm.exe
//
// Value = notepad.exe
// Value = paint.exe
// Value = paint.exe
// Value = winword.exe
// Value = winword.exe
// Value = hypertrm.exe
//
// Key = txt
// Key = bmp
// Key = dib
// Key = rtf
// Key = doc
// Key = ht
//
// Remove("doc")
// Key "doc" is not found.
Imports System.Collections.Generic
Public Class Example
Public Shared Sub Main()
' Create a new dictionary of strings, with string keys.
'
Dim openWith As New Dictionary(Of 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
Console.WriteLine("An element with Key = ""txt"" already exists.")
End Try
' The Item property is the default property, so you
' can omit its name when accessing elements.
Console.WriteLine("For key = ""rtf"", value = {0}.", _
openWith("rtf"))
' The default Item property 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 default Item property
' for that key adds a new key/value pair.
openWith("doc") = "winword.exe"
' The default Item property throws an exception if the requested
' key is not in the dictionary.
Try
Console.WriteLine("For key = ""tif"", value = {0}.", _
openWith("tif"))
Catch
Console.WriteLine("Key = ""tif"" is not found.")
End Try
' 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.
Dim value As String = ""
If openWith.TryGetValue("tif", value) Then
Console.WriteLine("For key = ""tif"", value = {0}.", value)
Else
Console.WriteLine("Key = ""tif"" is not found.")
End If
' ContainsKey can be used to test keys before inserting
' them.
If Not openWith.ContainsKey("ht") Then
openWith.Add("ht", "hypertrm.exe")
Console.WriteLine("Value added for key = ""ht"": {0}", _
openWith("ht"))
End If
' When you use foreach to enumerate dictionary elements,
' the elements are retrieved as KeyValuePair objects.
Console.WriteLine()
For Each kvp As KeyValuePair(Of String, String) In openWith
Console.WriteLine("Key = {0}, Value = {1}", _
kvp.Key, kvp.Value)
Next kvp
' To get the values alone, use the Values property.
Dim valueColl As _
Dictionary(Of String, String).ValueCollection = _
openWith.Values
' The elements of the ValueCollection are strongly typed
' with the type that was specified for dictionary values.
Console.WriteLine()
For Each s As String In valueColl
Console.WriteLine("Value = {0}", s)
Next s
' To get the keys alone, use the Keys property.
Dim keyColl As _
Dictionary(Of String, String).KeyCollection = _
openWith.Keys
' The elements of the KeyCollection are strongly typed
' with the type that was specified for dictionary keys.
Console.WriteLine()
For Each s As String In keyColl
Console.WriteLine("Key = {0}", s)
Next s
' Use the Remove method to remove a key/value pair.
Console.WriteLine(vbLf + "Remove(""doc"")")
openWith.Remove("doc")
If Not openWith.ContainsKey("doc") Then
Console.WriteLine("Key ""doc"" is not found.")
End If
End Sub
End Class
' This code example produces the following output:
'
'An element with Key = "txt" already exists.
'For key = "rtf", value = wordpad.exe.
'For key = "rtf", value = winword.exe.
'Key = "tif" is not found.
'Key = "tif" is not found.
'Value added for key = "ht": hypertrm.exe
'
'Key = txt, Value = notepad.exe
'Key = bmp, Value = paint.exe
'Key = dib, Value = paint.exe
'Key = rtf, Value = winword.exe
'Key = doc, Value = winword.exe
'Key = ht, Value = hypertrm.exe
'
'Value = notepad.exe
'Value = paint.exe
'Value = paint.exe
'Value = winword.exe
'Value = winword.exe
'Value = hypertrm.exe
'
'Key = txt
'Key = bmp
'Key = dib
'Key = rtf
'Key = doc
'Key = ht
'
'Remove("doc")
'Key "doc" is not found.
'
注解
Dictionary<TKey,TValue> 泛型类提供从一组键到一组值的映射。 字典的每个添加都包含一个值及其关联的键。 通过使用其键检索值非常快，接近 O（1），因为 Dictionary<TKey,TValue> 类作为哈希表实现。
注意
检索速度取决于为 TKey指定的类型的哈希算法的质量。
只要对象用作 Dictionary<TKey,TValue>中的键，它就不能以任何方式更改影响其哈希值。 根据字典的相等比较器，Dictionary<TKey,TValue> 中的每个键都必须是唯一的。 如果键的类型 TValue 为引用类型，则键不能 null，但值可以是。
Dictionary<TKey,TValue> 需要相等实现来确定键是否相等。 可以使用接受 comparer 参数的构造函数指定 IEqualityComparer<T> 泛型接口的实现;如果未指定实现，则使用默认泛型相等比较器 EqualityComparer<T>.Default。 如果类型 TKey 实现 System.IEquatable<T> 泛型接口，则默认相等比较器使用该实现。
注意
例如，可以使用 StringComparer 类提供的不区分大小写的字符串比较器来创建包含不区分大小写的字符串键的字典。
Dictionary<TKey,TValue> 的容量是 Dictionary<TKey,TValue> 可以保留的元素数。 随着元素添加到 Dictionary<TKey,TValue>，重新分配内部数组，容量会根据需要自动增加。
仅 .NET Framework： 对于非常大的 Dictionary<TKey,TValue> 对象，可以通过将 <gcAllowVeryLargeObjects> 配置元素的 enabled 属性设置为在运行时环境中 true，将 64 位系统上的最大容量增加到 20 亿个元素。
为了进行枚举，字典中的每个项都被视为表示值及其键的 KeyValuePair<TKey,TValue> 结构。 返回项的顺序未定义。
C# 语言的 foreach 语句（for each 在 C++ 中，在 Visual Basic 中 For Each）返回集合中元素类型的对象。 由于 Dictionary<TKey,TValue> 是键和值的集合，因此元素类型不是键的类型或值的类型。 相反，元素类型是键类型和值类型的 KeyValuePair<TKey,TValue>。 例如：
for each(KeyValuePair<String^, String^> kvp in myDictionary)
{
Console::WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}
foreach( KeyValuePair<string, string> kvp in myDictionary )
{
Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}
for kvp in myDictionary do
printfn $"Key = {kvp.Key}, Value = {kvp.Value}"
For Each kvp As KeyValuePair(Of String, String) In myDictionary
Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value)
Next kvp
foreach 语句是枚举器周围的包装器，它只允许从集合中读取，而不是写入集合。
注意
由于可以继承密钥并更改其行为，因此使用 Equals 方法的比较无法保证其绝对唯一性。
构造函数
属性
| Capacity |
获取内部数据结构可以保留的元素总数，而无需调整大小。 |
| Comparer |
获取用于确定字典键相等性的 IEqualityComparer<T>。 |
| Count |
获取 Dictionary<TKey,TValue>中包含的键/值对数。 |
| Item[TKey] |
获取或设置与指定键关联的值。 |
| Keys |
获取包含 Dictionary<TKey,TValue>中的键的集合。 |
| Values |
获取一个集合，该集合包含 Dictionary<TKey,TValue>中的值。 |
方法
| Add(TKey, TValue) |
将指定的键和值添加到字典。 |
| Clear() |
从 Dictionary<TKey,TValue>中删除所有键和值。 |
| ContainsKey(TKey) |
确定 Dictionary<TKey,TValue> 是否包含指定的键。 |
| ContainsValue(TValue) |
确定 Dictionary<TKey,TValue> 是否包含特定值。 |
| EnsureCapacity(Int32) |
确保字典可以容纳指定数量的条目，而无需进一步扩展其后盾存储。 |
| Equals(Object) |
确定指定的对象是否等于当前对象。 (继承自 Object) |
| GetEnumerator() |
返回循环访问 Dictionary<TKey,TValue>的枚举数。 |
| GetHashCode() |
用作默认哈希函数。 (继承自 Object) |
| GetObjectData(SerializationInfo, StreamingContext) |
已过时.
实现 ISerializable 接口并返回序列化 Dictionary<TKey,TValue> 实例所需的数据。 |
| GetType() |
获取当前实例的 Type。 (继承自 Object) |
| MemberwiseClone() |
创建当前 Object的浅表副本。 (继承自 Object) |
| OnDeserialization(Object) |
实现 ISerializable 接口，并在反序列化完成时引发反序列化事件。 |
| Remove(TKey) |
从 Dictionary<TKey,TValue>中删除具有指定键的值。 |
| Remove(TKey, TValue) |
从 Dictionary<TKey,TValue>中删除具有指定键的值，并将元素复制到 |
| ToString() |
返回一个表示当前对象的字符串。 (继承自 Object) |
| TrimExcess() |
将此字典的容量设置为最初使用其所有条目进行初始化时应采用的容量。 |
| TrimExcess(Int32) |
设置此字典的容量，以保留指定数量的条目，而无需进一步扩展其后盾存储。 |
| TryAdd(TKey, TValue) |
尝试将指定的键和值添加到字典。 |
| TryGetValue(TKey, TValue) |
获取与指定键关联的值。 |
显式接口实现
扩展方法
适用于
线程安全性
只要集合未修改，Dictionary<TKey,TValue> 就可以同时支持多个读取器。 即便如此，通过集合进行枚举本质上不是线程安全的过程。 在枚举与写入访问竞争的极少数情况下，必须在整个枚举期间锁定集合。 若要允许多个线程访问集合进行读取和写入，必须实现自己的同步。
有关线程安全的替代方法，请参阅 ConcurrentDictionary<TKey,TValue> 类或 ImmutableDictionary<TKey,TValue> 类。
此类型的公共静态（Shared）成员是线程安全的。
