List<T> Constructor (Int32)
Initializes a new instance of the List<T> class that is empty and has the specified initial capacity.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- capacity
-
Type:
System.Int32
The number of elements that the new list can initially store.
| Exception | Condition |
|---|---|
| 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 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 Main() { List<string> dinosaurs = new List<string>(4); Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity); dinosaurs.Add("Tyrannosaurus"); dinosaurs.Add("Amargasaurus"); dinosaurs.Add("Mamenchisaurus"); dinosaurs.Add("Deinonychus"); Console.WriteLine(); foreach(string s in dinosaurs) { Console.WriteLine(s); } Console.WriteLine("\nIList<string> roDinosaurs = dinosaurs.AsReadOnly()"); IList<string> roDinosaurs = dinosaurs.AsReadOnly(); Console.WriteLine("\nElements in the read-only IList:"); foreach(string dinosaur in roDinosaurs) { Console.WriteLine(dinosaur); } Console.WriteLine("\ndinosaurs[2] = \"Coelophysis\""); dinosaurs[2] = "Coelophysis"; Console.WriteLine("\nElements in the read-only IList:"); foreach(string dinosaur in roDinosaurs) { Console.WriteLine(dinosaur); } } } /* 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 */
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1