Dictionary<TKey, TValue> Constructor (Int32)
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Initializes a new instance of the Dictionary<TKey, TValue> class that is empty, has the specified 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 ( _
capacity As Integer _
)
public Dictionary(
int capacity
)
Parameters
- capacity
Type: System.Int32
The initial number of elements that the Dictionary<TKey, TValue> can contain.
Remarks
Every key in a Dictionary<TKey, TValue> must be unique according to the default equality comparer.
The capacity of a Dictionary<TKey, TValue> is the number of elements that can be added to the Dictionary<TKey, TValue> before resizing is necessary. As elements are added to a Dictionary<TKey, TValue>, the capacity is automatically increased as required by reallocating the internal array.
If the size of the collection can be estimated, specifying the initial capacity eliminates the need to perform a number of resizing operations while adding elements to the Dictionary<TKey, TValue>.
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.
This constructor is an O(1) operation.
Examples
The following code example creates a dictionary with an initial capacity of 4 and populates it with 4 entries.
Imports System.Collections.Generic
Public Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
' Create a new dictionary of strings, with string keys and
' an initial capacity of 4.
Dim openWith As New Dictionary(Of String, String)(4)
' Add 4 elements to the dictionary.
openWith.Add("txt", "notepad.exe")
openWith.Add("bmp", "paint.exe")
openWith.Add("dib", "paint.exe")
openWith.Add("rtf", "wordpad.exe")
' List the contents of the dictionary.
outputBlock.Text &= vbCrLf
For Each kvp As KeyValuePair(Of String, String) In openWith
outputBlock.Text &= String.Format("Key = {0}, Value = {1}", _
kvp.Key, kvp.Value) & vbCrLf
Next kvp
End Sub
End Class
' This code example produces the following output:
'
'Key = txt, Value = notepad.exe
'Key = bmp, Value = paint.exe
'Key = dib, Value = paint.exe
'Key = rtf, Value = wordpad.exe
using System;
using System.Collections.Generic;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
// Create a new dictionary of strings, with string keys and
// an initial capacity of 4.
Dictionary<string, string> openWith =
new Dictionary<string, string>(4);
// Add 4 elements to the dictionary.
openWith.Add("txt", "notepad.exe");
openWith.Add("bmp", "paint.exe");
openWith.Add("dib", "paint.exe");
openWith.Add("rtf", "wordpad.exe");
// List the contents of the dictionary.
outputBlock.Text += "\n";
foreach (KeyValuePair<string, string> kvp in openWith)
{
outputBlock.Text += String.Format("Key = {0}, Value = {1}",
kvp.Key, kvp.Value) + "\n";
}
}
}
/* This code example produces the following output:
Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = wordpad.exe
*/
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.