Sets the capacity to the actual number of elements in the List<(Of <(T>)>), if that number is less than a threshold value.
(in mscorlib.dll)
Visual Basic (Declaration)
Dim instance As List
instance.TrimExcess()
public:
void TrimExcess()
public function TrimExcess()
This method can be used to minimize a collection's memory overhead if no new elements will be added to the collection. The cost of reallocating and copying a large List<(Of <(T>)>) can be considerable, however, so the TrimExcess method does nothing if the list is at more than 90 percent of capacity. This avoids incurring a large reallocation cost for a relatively small gain.
.gif) Note: |
|---|
The current threshold of 90 percent might change in future releases. |
This method is an O(n) operation, where n is Count.
To reset a List<(Of <(T>)>) to its initial state, call the Clear method before calling the TrimExcess method. Trimming an empty List<(Of <(T>)>) sets the capacity of the List<(Of <(T>)>) to the default capacity.
The capacity can also be set using the Capacity property.
The following code example demonstrates the TrimExcess method. Several properties and methods of the List<(Of <(T>)>) class are used to add, insert, and remove items from a list of strings. Then the TrimExcess method is used to reduce the capacity to match the count, and the Capacity and Count properties are displayed. If the unused capacity had been less than 10 percent of total capacity, the list would not have been resized. Finally, the contents of the list are cleared.
Imports System
Imports System.Collections.Generic
Public Class Example
Public Shared Sub Main()
Dim dinosaurs As New List(Of String)
Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity)
dinosaurs.Add("Tyrannosaurus")
dinosaurs.Add("Amargasaurus")
dinosaurs.Add("Mamenchisaurus")
dinosaurs.Add("Deinonychus")
dinosaurs.Add("Compsognathus")
Console.WriteLine()
For Each dinosaur As String In dinosaurs
Console.WriteLine(dinosaur)
Next
Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity)
Console.WriteLine("Count: {0}", dinosaurs.Count)
Console.WriteLine(vbLf & "Contains(""Deinonychus""): {0}", _
dinosaurs.Contains("Deinonychus"))
Console.WriteLine(vbLf & "Insert(2, ""Compsognathus"")")
dinosaurs.Insert(2, "Compsognathus")
Console.WriteLine()
For Each dinosaur As String In dinosaurs
Console.WriteLine(dinosaur)
Next
Console.WriteLine(vbLf & "dinosaurs(3): {0}", dinosaurs(3))
Console.WriteLine(vbLf & "Remove(""Compsognathus"")")
dinosaurs.Remove("Compsognathus")
Console.WriteLine()
For Each dinosaur As String In dinosaurs
Console.WriteLine(dinosaur)
Next
dinosaurs.TrimExcess()
Console.WriteLine(vbLf & "TrimExcess()")
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity)
Console.WriteLine("Count: {0}", dinosaurs.Count)
dinosaurs.Clear()
Console.WriteLine(vbLf & "Clear()")
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity)
Console.WriteLine("Count: {0}", dinosaurs.Count)
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
using System;
using System.Collections.Generic;
public class Example
{
public static void Main()
{
List<string> dinosaurs = new List<string>();
Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);
dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Mamenchisaurus");
dinosaurs.Add("Deinonychus");
dinosaurs.Add("Compsognathus");
Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);
Console.WriteLine("\nContains(\"Deinonychus\"): {0}",
dinosaurs.Contains("Deinonychus"));
Console.WriteLine("\nInsert(2, \"Compsognathus\")");
dinosaurs.Insert(2, "Compsognathus");
Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]);
Console.WriteLine("\nRemove(\"Compsognathus\")");
dinosaurs.Remove("Compsognathus");
Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
dinosaurs.TrimExcess();
Console.WriteLine("\nTrimExcess()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);
dinosaurs.Clear();
Console.WriteLine("\nClear()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);
}
}
/* 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
*/
using namespace System;
using namespace System::Collections::Generic;
void main()
{
List<String^>^ dinosaurs = gcnew List<String^>();
Console::WriteLine("\nCapacity: {0}", dinosaurs->Capacity);
dinosaurs->Add("Tyrannosaurus");
dinosaurs->Add("Amargasaurus");
dinosaurs->Add("Mamenchisaurus");
dinosaurs->Add("Deinonychus");
dinosaurs->Add("Compsognathus");
Console::WriteLine();
for each(String^ dinosaur in dinosaurs )
{
Console::WriteLine(dinosaur);
}
Console::WriteLine("\nCapacity: {0}", dinosaurs->Capacity);
Console::WriteLine("Count: {0}", dinosaurs->Count);
Console::WriteLine("\nContains(\"Deinonychus\"): {0}",
dinosaurs->Contains("Deinonychus"));
Console::WriteLine("\nInsert(2, \"Compsognathus\")");
dinosaurs->Insert(2, "Compsognathus");
Console::WriteLine();
for each(String^ dinosaur in dinosaurs )
{
Console::WriteLine(dinosaur);
}
Console::WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]);
Console::WriteLine("\nRemove(\"Compsognathus\")");
dinosaurs->Remove("Compsognathus");
Console::WriteLine();
for each(String^ dinosaur in dinosaurs )
{
Console::WriteLine(dinosaur);
}
dinosaurs->TrimExcess();
Console::WriteLine("\nTrimExcess()");
Console::WriteLine("Capacity: {0}", dinosaurs->Capacity);
Console::WriteLine("Count: {0}", dinosaurs->Count);
dinosaurs->Clear();
Console::WriteLine("\nClear()");
Console::WriteLine("Capacity: {0}", dinosaurs->Capacity);
Console::WriteLine("Count: {0}", dinosaurs->Count);
}
/* 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
*/
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5, 3.0, 2.0
.NET Compact Framework
Supported in: 3.5, 2.0
XNA Framework
Supported in: 3.0, 2.0, 1.0
Reference