Dictionary<TKey, TValue> Constructor
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Initializes a new instance of the Dictionary<TKey, TValue> class that is empty, has the default initial capacity, and uses the default equality comparer for the key type.
Namespace: System.Collections.Generic
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Sub New
public Dictionary()
Remarks
Every key in a Dictionary<TKey, TValue> must be unique according to the default equality comparer.
Dictionary<TKey, TValue> requires an equality implementation to determine whether keys are equal. This constructor uses the default generic equality comparer, EqualityComparer<T>.Default. If type TKey implements the System.IEquatable<T> generic interface, the default equality comparer uses that implementation. Alternatively, you can specify an implementation of the IEqualityComparer<T> generic interface by using a constructor that accepts a comparer parameter.
.gif "Note") Note: |
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If you can estimate the size of the collection, using a constructor that specifies the initial capacity eliminates the need to perform a number of resizing operations while adding elements to the Dictionary<TKey, TValue>. |
This constructor is an O(1) operation.
Examples
The following code example creates an empty Dictionary<TKey, TValue> of strings with string keys and uses the Add method to add some elements. The example demonstrates that the Add method throws an ArgumentException when attempting to add a duplicate key.
This code example is part of a larger example provided for the Dictionary<TKey, TValue> class.
' 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
outputBlock.Text &= "An element with Key = ""txt"" already exists." & vbCrLf
End Try
// 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)
{
outputBlock.Text += "An element with Key = \"txt\" already exists." + "\n";
}
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.