Dictionary<TKey,TValue>.ContainsKey(TKey) Dictionary<TKey,TValue>.ContainsKey(TKey) Dictionary<TKey,TValue>.ContainsKey(TKey) Dictionary<TKey,TValue>.ContainsKey(TKey) Method

Définition

Détermine si Dictionary<TKey,TValue> contient la clé spécifiée.Determines whether the Dictionary<TKey,TValue> contains the specified key.

public:
 virtual bool ContainsKey(TKey key);
public bool ContainsKey (TKey key);
abstract member ContainsKey : 'Key -> bool
override this.ContainsKey : 'Key -> bool
Public Function ContainsKey (key As TKey) As Boolean

Paramètres

key
TKey TKey TKey TKey

Clé à rechercher dans Dictionary<TKey,TValue>.The key to locate in the Dictionary<TKey,TValue>.

Retours

true si Dictionary<TKey,TValue> contient un élément correspondant à la clé spécifiée ; sinon, false.true if the Dictionary<TKey,TValue> contains an element with the specified key; otherwise, false.

Implémente

Exceptions

Exemples

L’exemple de code suivant montre comment utiliser la ContainsKey méthode pour tester si une clé existe avant d’appeler la Add méthode.The following code example shows how to use the ContainsKey method to test whether a key exists prior to calling the Add method. Il montre également comment utiliser la TryGetValue méthode pour récupérer des valeurs, ce qui constitue un moyen efficace pour récupérer des valeurs lorsqu’un programme tente fréquemment des clés qui ne sont pas dans le dictionnaire.It also shows how to use the TryGetValue method to retrieve values, which is an efficient way to retrieve values when a program frequently tries keys that are not in the dictionary. Enfin, il montre le moyen le moins efficace de tester si les clés existent, à Item[TKey] l’aide de la propriété ( C#l’indexeur dans).Finally, it shows the least efficient way to test whether keys exist, by using the Item[TKey] property (the indexer in C#).

Cet exemple de code fait partie d’un exemple plus complet fourni Dictionary<TKey,TValue> pour laopenWith classe (est le nom du dictionnaire utilisé dans cet exemple).This code example is part of a larger example provided for the Dictionary<TKey,TValue> class (openWith is the name of the Dictionary used in this example).

// 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"]);
}
// 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"]);
}
' 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 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.");
}
// 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.");
}
' 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
// 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.");
}
// 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.");
}
' 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

Remarques

Cette méthode s’approche d’une opération O (1).This method approaches an O(1) operation.

S’applique à

Voir aussi