List(Of T).Capacity Property
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Gets or sets the total number of elements the internal data structure can hold without resizing.
Assembly: mscorlib (in mscorlib.dll)
Property Value
Type: System.Int32The number of elements that the List(Of T) can contain before resizing is required.
| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | Capacity is set to a value that is less than Count. |
| OutOfMemoryException | There is not enough memory available on the system. |
Capacity is the number of elements that the List(Of T) can store before resizing is required, while Count is the number of elements that are actually in the List(Of T).
Capacity is always greater than or equal to Count. If Count exceeds Capacity while adding elements, the capacity is increased by automatically reallocating the internal array before copying the old elements and adding the new elements.
The capacity can be decreased by calling the TrimExcess method or by setting the Capacity property explicitly. When the value of Capacity is set explicitly, the internal array is also reallocated to accommodate the specified capacity, and all the elements are copied.
Retrieving the value of this property is an O(1) operation; setting the property is an O(n) operation, where n is the new capacity.
The following code example shows the Capacity property at several points in the life of a list. The default constructor is used to create a list of strings with a capacity of 0, and the Capacity property is displayed to demonstrate this. After the Add method has been used to add several items, the items are listed, and then the Capacity property is displayed again, along with the Count property, to show that the capacity has been increased as needed.
The Capacity property is displayed again after the TrimExcess method is used to reduce the capacity to match the count. Finally, the Clear method is used to remove all items from the list, and the Capacity and Count properties are displayed again.
Imports System.Collections.Generic Public Class Example Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) Dim dinosaurs As New List(Of String) outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf dinosaurs.Add("Tyrannosaurus") dinosaurs.Add("Amargasaurus") dinosaurs.Add("Mamenchisaurus") dinosaurs.Add("Deinonychus") dinosaurs.Add("Compsognathus") outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf outputBlock.Text &= vbLf & String.Format("Contains(""Deinonychus"": {0}", _ dinosaurs.Contains("Deinonychus")) & vbCrLf outputBlock.Text &= String.Format(vbLf & "Insert(2, ""Compsognathus"")") & vbCrLf dinosaurs.Insert(2, "Compsognathus") outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next outputBlock.Text &= String.Format(vbLf & "dinosaurs(3): {0}", dinosaurs(3)) & vbCrLf outputBlock.Text &= vbLf & "Remove(""Compsognathus"")" & vbCrLf dinosaurs.Remove("Compsognathus") outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next dinosaurs.TrimExcess() outputBlock.Text &= vbLf & "TrimExcess()" & vbCrLf outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf dinosaurs.Clear() outputBlock.Text &= vbLf & "Clear()" & vbCrLf outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf End Sub End Class ' This code example produces the following output: ' 'Capacity: 0 ' 'Tyrannosaurus 'Amargasaurus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'Capacity: 8 'Count: 5 ' 'Contains("Deinonychus"): True ' 'Insert(2, "Compsognathus") ' 'Tyrannosaurus 'Amargasaurus 'Compsognathus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'dinosaurs(3): Mamenchisaurus ' 'Remove("Compsognathus") ' 'Tyrannosaurus 'Amargasaurus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'TrimExcess() 'Capacity: 5 'Count: 5 ' 'Clear() 'Capacity: 5 'Count: 0