SortedDictionary<TKey,TValue>.IDictionary.Add(Object, Object) 方法
定义
重要
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向 IDictionary 添加一个带有所提供的键和值的元素。
virtual void System.Collections.IDictionary.Add(System::Object ^ key, System::Object ^ value) = System::Collections::IDictionary::Add;void IDictionary.Add (object key, object value);abstract member System.Collections.IDictionary.Add : obj * obj -> unit
override this.System.Collections.IDictionary.Add : obj * obj -> unitSub Add (key As Object, value As Object) Implements IDictionary.Add参数
- key
- Object
用作要添加的元素的键的对象。
- value
- Object
用作要添加的元素的值的对象。
实现
例外
key 为 null。
key 属于不能分配给 IDictionary 的键类型 TKey 的类型。
- 或 -
value 属于不能分配给 IDictionary 的值类型 TValue 的类型。
- 或 -
IDictionary 中已存在具有相同键的元素。
示例
下面的代码示例演示如何通过 System.Collections.IDictionary 接口访问 SortedDictionary<TKey,TValue> 类。 该代码示例使用字符串键创建一个空 SortedDictionary<TKey,TValue> 字符串，并使用 IDictionary.Add 方法添加一些元素。 该示例演示 IDictionary.Add 方法在尝试添加重复键或提供错误数据类型的键或值时引发 ArgumentException 。
该代码示例演示如何使用 接口的多个其他成员 System.Collections.IDictionary 。
using System;
using System.Collections;
using System.Collections.Generic;
public class Example
{
public static void Main()
{
// Create a new sorted dictionary of strings, with string keys,
// and access it using the IDictionary interface.
//
IDictionary openWith = new SortedDictionary<string, string>();
// Add some elements to the dictionary. There are no
// duplicate keys, but some of the values are duplicates.
// IDictionary.Add throws an exception if incorrect types
// are supplied for key or value.
openWith.Add("txt", "notepad.exe");
openWith.Add("bmp", "paint.exe");
openWith.Add("dib", "paint.exe");
openWith.Add("rtf", "wordpad.exe");
try
{
openWith.Add(42, new Example());
}
catch (ArgumentException ex)
{
Console.WriteLine("An exception was caught for " +
"IDictionary.Add. Exception message:\n\t{0}\n",
ex.Message);
}
// 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 returns null if the key is of the wrong data
// type.
Console.WriteLine("The indexer returns null"
+ " if the key is of the wrong type:");
Console.WriteLine("For key = 2, value = {0}.",
openWith[2]);
// The indexer throws an exception when setting a value
// if the key is of the wrong data type.
try
{
openWith[2] = "This does not get added.";
}
catch (ArgumentException)
{
Console.WriteLine("A key of the wrong type was specified"
+ " when assigning to the indexer.");
}
// Unlike the default Item property on the Dictionary class
// itself, IDictionary.Item does not throw an exception
// if the requested key is not in the dictionary.
Console.WriteLine("For key = \"tif\", value = {0}.",
openWith["tif"]);
// Contains can be used to test keys before inserting
// them.
if (!openWith.Contains("ht"))
{
openWith.Add("ht", "hypertrm.exe");
Console.WriteLine("Value added for key = \"ht\": {0}",
openWith["ht"]);
}
// IDictionary.Contains returns false if the wrong data
// type is supplied.
Console.WriteLine("openWith.Contains(29.7) returns {0}",
openWith.Contains(29.7));
// When you use foreach to enumerate dictionary elements
// with the IDictionary interface, the elements are retrieved
// as DictionaryEntry objects instead of KeyValuePair objects.
Console.WriteLine();
foreach( DictionaryEntry de in openWith )
{
Console.WriteLine("Key = {0}, Value = {1}",
de.Key, de.Value);
}
// To get the values alone, use the Values property.
ICollection icoll = openWith.Values;
// The elements of the collection are strongly typed
// with the type that was specified for dictionary values,
// even though the ICollection interface is not strongly
// typed.
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 collection are strongly typed
// with the type that was specified for dictionary keys,
// even though the ICollection interface is not strongly
// typed.
Console.WriteLine();
foreach( string s in icoll )
{
Console.WriteLine("Key = {0}", s);
}
// Use the Remove method to remove a key/value pair. No
// exception is thrown if the wrong data type is supplied.
Console.WriteLine("\nRemove(\"dib\")");
openWith.Remove("dib");
if (!openWith.Contains("dib"))
{
Console.WriteLine("Key \"dib\" is not found.");
}
}
}
/* This code example produces the following output:
An exception was caught for IDictionary.Add. Exception message:
The value "42" is not of type "System.String" and cannot be used in this generic collection.
Parameter name: key
An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
The indexer returns null if the key is of the wrong type:
For key = 2, value = .
A key of the wrong type was specified when assigning to the indexer.
For key = "tif", value = .
Value added for key = "ht": hypertrm.exe
openWith.Contains(29.7) returns False
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe
Key = rtf, Value = winword.exe
Key = txt, Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = hypertrm.exe
Value = winword.exe
Value = notepad.exe
Key = bmp
Key = dib
Key = doc
Key = ht
Key = rtf
Key = txt
Remove("dib")
Key "dib" is not found.
*/
Imports System.Collections
Imports System.Collections.Generic
Public Class Example
Public Shared Sub Main()
' Create a new sorted dictionary of strings, with string keys,
' and access it using the IDictionary interface.
'
Dim openWith As IDictionary = _
New SortedDictionary(Of String, String)
' Add some elements to the dictionary. There are no
' duplicate keys, but some of the values are duplicates.
' IDictionary.Add throws an exception if incorrect types
' are supplied for key or value.
openWith.Add("txt", "notepad.exe")
openWith.Add("bmp", "paint.exe")
openWith.Add("dib", "paint.exe")
openWith.Add("rtf", "wordpad.exe")
Try
openWith.Add(42, New Example())
Catch ex As ArgumentException
Console.WriteLine("An exception was caught for " & _
"IDictionary.Add. Exception message:" & vbLf _
& vbTab & ex.Message & vbLf)
End Try
' 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 returns Nothing if the key
' is of the wrong data type.
Console.WriteLine("The default Item property returns Nothing" _
& " if the key is of the wrong type:")
Console.WriteLine("For key = 2, value = {0}.", _
openWith(2))
' The default Item property throws an exception when setting
' a value if the key is of the wrong data type.
Try
openWith(2) = "This does not get added."
Catch
Console.WriteLine("A key of the wrong type was specified" _
& " when setting the default Item property.")
End Try
' Unlike the default Item property on the Dictionary class
' itself, IDictionary.Item does not throw an exception
' if the requested key is not in the dictionary.
Console.WriteLine("For key = ""tif"", value = {0}.", _
openWith("tif"))
' Contains can be used to test keys before inserting
' them.
If Not openWith.Contains("ht") Then
openWith.Add("ht", "hypertrm.exe")
Console.WriteLine("Value added for key = ""ht"": {0}", _
openWith("ht"))
End If
' IDictionary.Contains returns False if the wrong data
' type is supplied.
Console.WriteLine("openWith.Contains(29.7) returns {0}", _
openWith.Contains(29.7))
' When you use foreach to enumerate dictionary elements
' with the IDictionary interface, the elements are retrieved
' as DictionaryEntry objects instead of KeyValuePair objects.
Console.WriteLine()
For Each de As DictionaryEntry In openWith
Console.WriteLine("Key = {0}, Value = {1}", _
de.Key, de.Value)
Next
' To get the values alone, use the Values property.
Dim icoll As ICollection = openWith.Values
' The elements of the collection are strongly typed
' with the type that was specified for dictionary values,
' even though the ICollection interface is not strongly
' typed.
Console.WriteLine()
For Each s As String In icoll
Console.WriteLine("Value = {0}", s)
Next s
' To get the keys alone, use the Keys property.
icoll = openWith.Keys
' The elements of the collection are strongly typed
' with the type that was specified for dictionary keys,
' even though the ICollection interface is not strongly
' typed.
Console.WriteLine()
For Each s As String In icoll
Console.WriteLine("Key = {0}", s)
Next s
' Use the Remove method to remove a key/value pair. No
' exception is thrown if the wrong data type is supplied.
Console.WriteLine(vbLf + "Remove(""dib"")")
openWith.Remove("dib")
If Not openWith.Contains("dib") Then
Console.WriteLine("Key ""dib"" is not found.")
End If
End Sub
End Class
' This code example produces the following output:
'
'An exception was caught for IDictionary.Add. Exception message:
' The value "42" is not of type "System.String" and cannot be used in this generic collection.
'Parameter name: key
'
'An element with Key = "txt" already exists.
'For key = "rtf", value = wordpad.exe.
'For key = "rtf", value = winword.exe.
'The default Item property returns Nothing if the key is of the wrong type:
'For key = 2, value = .
'A key of the wrong type was specified when setting the default Item property.
'For key = "tif", value = .
'Value added for key = "ht": hypertrm.exe
'openWith.Contains(29.7) returns False
'
'Key = bmp, Value = paint.exe
'Key = dib, Value = paint.exe
'Key = doc, Value = winword.exe
'Key = ht, Value = hypertrm.exe
'Key = rtf, Value = winword.exe
'Key = txt, Value = notepad.exe
'
'Value = paint.exe
'Value = paint.exe
'Value = winword.exe
'Value = hypertrm.exe
'Value = winword.exe
'Value = notepad.exe
'
'Key = bmp
'Key = dib
'Key = doc
'Key = ht
'Key = rtf
'Key = txt
'
'Remove("dib")
'Key "dib" is not found.
'
注解
还可以使用 Item[] 属性通过设置字典中不存在的键的值来添加新元素;例如 。 myCollection["myNonexistentKey"] = myValue 但是，如果字典中已存在指定的键，则设置 Item[] 属性将覆盖旧值。 相反， Add 方法不修改现有元素。
此方法是 O (日志 n) 操作，其中 n 为 Count。
