StringDictionary.ContainsKey Method (String)
Determines if the StringDictionary contains a specific key.
Assembly: System (in System.dll)
Parameters
- key
-
Type:
System.String
The key to locate in the StringDictionary.
Return Value
Type: System.Booleantrue if the StringDictionary contains an entry with the specified key; otherwise, false.
| Exception | Condition |
|---|---|
| ArgumentNullException | The key is null. |
The key is handled in a case-insensitive manner; it is translated to lowercase before it is used.
This method is an O(1) operation.
Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.
The following code example searches for an element in a StringDictionary.
Imports System Imports System.Collections Imports System.Collections.Specialized Public Class SamplesStringDictionary Public Shared Sub Main() ' Creates and initializes a new StringDictionary. Dim myCol As New StringDictionary() myCol.Add("red", "rojo") myCol.Add("green", "verde") myCol.Add("blue", "azul") ' Displays the values in the StringDictionary. Console.WriteLine("Initial contents of the StringDictionary:") PrintKeysAndValues(myCol) ' Searches for a key. If myCol.ContainsKey("red") Then Console.WriteLine("The collection contains the key ""red"".") Else Console.WriteLine("The collection does not contain the key ""red"".") End If Console.WriteLine() ' Searches for a value. If myCol.ContainsValue("amarillo") Then Console.WriteLine("The collection contains the value ""amarillo"".") Else Console.WriteLine("The collection does not contain the value ""amarillo"".") End If Console.WriteLine() End Sub 'Main Public Shared Sub PrintKeysAndValues(myCol As StringDictionary) Dim de As DictionaryEntry Console.WriteLine(" KEY VALUE") For Each de In myCol Console.WriteLine(" {0,-10} {1}", de.Key, de.Value) Next de Console.WriteLine() End Sub 'PrintKeysAndValues End Class 'SamplesStringDictionary 'This code produces the following output. ' 'Initial contents of the StringDictionary: ' KEY VALUE ' green verde ' red rojo ' blue azul ' 'The collection contains the key "red". ' 'The collection does not contain the value "amarillo".
Available since 10
.NET Framework
Available since 1.1