IDictionary<TKey,TValue>.Add(TKey, TValue) 方法

定義

命名空間:

System.Collections.Generic

組件:

System.Runtime.dll

將隨附有索引鍵和值的項目加入至 IDictionary<TKey,TValue>。

public:
 void Add(TKey key, TValue value);

public void Add (TKey key, TValue value);

abstract member Add : 'Key * 'Value -> unit

Public Sub Add (key As TKey, value As TValue)

參數

key

TKey

做為要加入項目之索引鍵的物件。

value

TValue

做為要加入項目之值的物件。

例外狀況

ArgumentNullException

key 為 null。

ArgumentException

IDictionary<TKey,TValue> 中已存在具有相同索引鍵的元素。

NotSupportedException

IDictionary<TKey,TValue> 為唯讀。

範例

下列程式代碼範例會使用整數索引鍵建立字串的空白 Dictionary<TKey,TValue> ，並透過 IDictionary<TKey,TValue> 介面加以存取。 程式代碼範例會 Add 使用 方法來新增一些元素。 此範例示範 Add 當嘗試加入重複索引鍵時，方法會 ArgumentException 擲回 。

此程式代碼是可編譯和執行之較大範例的一部分。 請參閱 System.Collections.Generic.IDictionary<TKey,TValue>。

// Create a new dictionary of strings, with string keys,
// and access it through the IDictionary generic interface.
IDictionary<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.");
}

// 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.");
}

' Create a new dictionary of strings, with string keys, 
' and access it through the IDictionary generic interface.
Dim openWith As IDictionary(Of String, String) = _
    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

備註

您也可以使用 Item[] 屬性來新增元素，方法是設定字典中不存在的索引鍵值;例如， myCollection["myNonexistentKey"] = myValue 在 Visual Basic) 的 C# (myCollection("myNonexistentKey") = myValue 中。 不過，如果指定的索引鍵已存在於字典中，則設定 Item[] 屬性會覆寫舊的值。 相反地， Add 方法不會修改現有的專案。

實作可能會因判斷物件的相等方式而有所不同;例如， List<T> 類別會使用 Comparer<T>.Default，而 Dictionary<TKey,TValue> 類別可讓使用者指定要 IComparer<T> 用於比較索引鍵的實作。

實作可能會因是否允許 key 為 null而有所不同。

另請參閱

• Item[TKey]
• IsReadOnly