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List(T).Sort Method (Int32, Int32, IComparer(T))

Sorts the elements in a range of elements in List(T) using the specified comparer.

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

public function Sort(
	index : int, 
	count : int, 
	comparer : IComparer<T>


Type: System.Int32

The zero-based starting index of the range to sort.

Type: System.Int32

The length of the range to sort.

Type: System.Collections.Generic.IComparer(T)

The IComparer(T) implementation to use when comparing elements, or a null reference (Nothing in Visual Basic) to use the default comparer Comparer(T).Default.


index is less than 0.


count is less than 0.


index and count do not specify a valid range in the List(T).


The implementation of comparer caused an error during the sort. For example, comparer might not return 0 when comparing an item with itself.


comparer is a null reference (Nothing in Visual Basic), and the default comparer Comparer(T).Default cannot find implementation of the IComparable(T) generic interface or the IComparable interface for type T.

If comparer is provided, the elements of the List(T) are sorted using the specified IComparer(T) implementation.

If comparer is a null reference (Nothing in Visual Basic), the default comparer Comparer(T).Default checks whether type T implements the IComparable(T) generic interface and uses that implementation, if available. If not, Comparer(T).Default checks whether type T implements the IComparable interface. If type T does not implement either interface, Comparer(T).Default throws an InvalidOperationException.

This method uses Array.Sort, which uses the QuickSort algorithm. This implementation performs an unstable sort; that is, if two elements are equal, their order might not be preserved. In contrast, a stable sort preserves the order of elements that are equal.

On average, this method is an O(n log n) operation, where n is Count; in the worst case it is an O(n ^ 2) operation.

The following code example demonstrates the Sort(Int32, Int32, IComparer(T)) method overload and the BinarySearch(Int32, Int32, T, IComparer(T)) method overload.

The code example defines an alternative comparer for strings named DinoCompare, which implements the IComparer<string> (IComparer(Of String) in Visual Basic, IComparer<String^> in Visual C++) generic interface. The comparer works as follows: First, the comparands are tested for a null reference (Nothing in Visual Basic), and a null reference is treated as less than a non-null. Second, the string lengths are compared, and the longer string is deemed to be greater. Third, if the lengths are equal, ordinary string comparison is used.

A List(T) of strings is created and populated with the names of five herbivorous dinosaurs and three carnivorous dinosaurs. Within each of the two groups, the names are not in any particular sort order. The list is displayed, the range of herbivores is sorted using the alternate comparer, and the list is displayed again.

The BinarySearch(Int32, Int32, T, IComparer(T)) method overload is then used to search only the range of herbivores for "Brachiosaurus". The string is not found, and the bitwise complement (the ~ operator in C# and Visual C++, Xor -1 in Visual Basic) of the negative number returned by the BinarySearch(Int32, Int32, T, IComparer(T)) method is used as an index for inserting the new string.

No code example is currently available or this language may not be supported.

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