List(Of T) Constructor (IEnumerable(Of T))
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Initializes a new instance of the List(Of T) class that contains elements copied from the specified collection and has sufficient capacity to accommodate the number of elements copied.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- collection
- Type: System.Collections.Generic.IEnumerable(Of T)
The collection whose elements are copied to the new list.
| Exception | Condition |
|---|---|
| ArgumentNullException | collection is Nothing. |
The capacity of a List(Of T) is the number of elements that the List(Of T) can hold. As elements are added to a List(Of 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(Of 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(Of T).
The elements are copied onto the List(Of T) in the same order they are read by the enumerator of the collection.
This constructor is an O(n) operation, where n is the number of elements in collection.
The following code example demonstrates the List(Of T) constructor and various methods of the List(Of T) class that act on ranges. An array of strings is created and passed to the constructor, populating the list with the elements of the array. The Capacity property is then displayed, to show that the initial capacity is exactly what is required to hold the input elements.
Imports System.Collections.Generic Public Class Example Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) Dim input() As String = {"Brachiosaurus", _ "Amargasaurus", _ "Mamenchisaurus"} Dim dinosaurs As New List(Of String)(input) outputBlock.Text += String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next outputBlock.Text &= vbLf & "AddRange(dinosaurs)" & vbCrLf dinosaurs.AddRange(dinosaurs) outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next outputBlock.Text += String.Format(vbLf & "RemoveRange(2, 2)") & vbCrLf dinosaurs.RemoveRange(2, 2) outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next input = New String() {"Tyrannosaurus", _ "Deinonychus", _ "Velociraptor"} outputBlock.Text += String.Format(vbLf & "InsertRange(3, input)") & vbCrLf dinosaurs.InsertRange(3, input) outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next outputBlock.Text += String.Format(vbLf & "output = dinosaurs.GetRange(2, 3).ToArray") & vbCrLf Dim output() As String = dinosaurs.GetRange(2, 3).ToArray() outputBlock.Text &= vbCrLf For Each dinosaur As String In output outputBlock.Text &= dinosaur & vbCrLf Next End Sub End Class ' This code example produces the following output: ' 'Capacity: 3 ' 'Brachiosaurus 'Amargasaurus 'Mamenchisaurus ' 'AddRange(dinosaurs) ' 'Brachiosaurus 'Amargasaurus 'Mamenchisaurus 'Brachiosaurus 'Amargasaurus 'Mamenchisaurus ' 'RemoveRange(2, 2) ' 'Brachiosaurus 'Amargasaurus 'Amargasaurus 'Mamenchisaurus ' 'InsertRange(3, input) ' 'Brachiosaurus 'Amargasaurus 'Amargasaurus 'Tyrannosaurus 'Deinonychus 'Velociraptor 'Mamenchisaurus ' 'output = dinosaurs.GetRange(2, 3).ToArray ' 'Amargasaurus 'Tyrannosaurus 'Deinonychus