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List<T> Constructor (Int32)

Initializes a new instance of the List<T> class that is empty and has the specified initial capacity.

Namespace:  System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)

public List(
	int capacity
)

Parameters

capacity
Type: System.Int32
The number of elements that the new list can initially store.

ExceptionCondition
ArgumentOutOfRangeException

capacity is less than 0.

The capacity of a List<T> is the number of elements that the List<T> can hold. As elements are added to a List<T>, 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 List<T>.

The capacity can be decreased by calling the TrimExcess method or by setting the Capacity property explicitly. Decreasing the capacity reallocates memory and copies all the elements in the List<T>.

This constructor is an O(n) operation, where n is capacity.

The following code example demonstrates the List<T>(Int32) constructor. A List<T> of strings with a capacity of 4 is created, because the ultimate size of the list is known to be exactly 4. The list is populated with four strings, and a read-only copy is created by using the AsReadOnly method.


using System;
using System.Collections.Generic;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      List<string> dinosaurs = new List<string>(4);

      outputBlock.Text += String.Format("\nCapacity: {0}", dinosaurs.Capacity) + "\n";

      dinosaurs.Add("Tyrannosaurus");
      dinosaurs.Add("Amargasaurus");
      dinosaurs.Add("Mamenchisaurus");
      dinosaurs.Add("Deinonychus");

      outputBlock.Text += "\n";
      foreach (string s in dinosaurs)
      {
         outputBlock.Text += s + "\n";
      }

      outputBlock.Text += "\nIList<string> roDinosaurs = dinosaurs.AsReadOnly()" + "\n";
      IList<string> roDinosaurs = dinosaurs.AsReadOnly();

      outputBlock.Text += "\nElements in the read-only IList:" + "\n";
      foreach (string dinosaur in roDinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

      outputBlock.Text += "\ndinosaurs[2] = \"Coelophysis\"" + "\n";
      dinosaurs[2] = "Coelophysis";

      outputBlock.Text += "\nElements in the read-only IList:" + "\n";
      foreach (string dinosaur in roDinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }
   }
}

/* This code example produces the following output:

Capacity: 4

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus

IList<string> roDinosaurs = dinosaurs.AsReadOnly()

Elements in the read-only IList:
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus

dinosaurs[2] = "Coelophysis"

Elements in the read-only IList:
Tyrannosaurus
Amargasaurus
Coelophysis
Deinonychus
 */


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

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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