SortedList Class

.NET Framework 4.5

Other Versions

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Represents a collection of key/value pairs that are sorted by the keys and are accessible by key and by index.

Inheritance Hierarchy

System .Object 
   System.Collections.SortedList

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

Syntax

The SortedList type exposes the following members.

Constructors

Show:  Inherited  Protected

	Name	Description
	SortedList()	Initializes a new instance of the SortedList class that is empty, has the default initial capacity, and is sorted according to the IComparable interface implemented by each key added to theSortedList object.
	SortedList(IComparer)	Initializes a new instance of the SortedList class that is empty, has the default initial capacity, and is sorted according to the specified IComparer interface.
	SortedList(IDictionary)	Initializes a new instance of the SortedList class that contains elements copied from the specified dictionary, has the same initial capacity as the number of elements copied, and is sorted according to the IComparable interface implemented by each key.
	SortedList(Int32)	Initializes a new instance of the SortedList class that is empty, has the specified initial capacity, and is sorted according to the IComparable interface implemented by each key added to theSortedList object.
	SortedList(IComparer, Int32)	Initializes a new instance of the SortedList class that is empty, has the specified initial capacity, and is sorted according to the specified IComparer interface.
	SortedList(IDictionary, IComparer)	Initializes a new instance of the SortedList class that contains elements copied from the specified dictionary, has the same initial capacity as the number of elements copied, and is sorted according to the specified IComparer interface.

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Properties

Show:  Inherited  Protected

	Name	Description
	Capacity	Gets or sets the capacity of a SortedList object.
	Count	Gets the number of elements contained in a SortedList object.
	IsFixedSize	Gets a value indicating whether a SortedList object has a fixed size.
	IsReadOnly	Gets a value indicating whether a SortedList object is read-only.
	IsSynchronized	Gets a value indicating whether access to a SortedList object is synchronized (thread safe).
	Item	Gets and sets the value associated with a specific key in a SortedList object.
	Keys	Gets the keys in a SortedList object.
	SyncRoot	Gets an object that can be used to synchronize access to a SortedList object.
	Values	Gets the values in a SortedList object.

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Methods

Show:  Inherited  Protected

	Name	Description
	Add	Adds an element with the specified key and value to a SortedList object.
	Clear	Removes all elements from a SortedList object.
	Clone	Creates a shallow copy of a SortedList object.
	Contains	Determines whether a SortedList object contains a specific key.
	ContainsKey	Determines whether a SortedList object contains a specific key.
	ContainsValue	Determines whether a SortedList object contains a specific value.
	CopyTo	Copies SortedList elements to a one-dimensional Array object, starting at the specified index in the array.
	Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetByIndex	Gets the value at the specified index of a SortedList object.
	GetEnumerator	Returns an IDictionaryEnumerator object that iterates through a SortedList object.
	GetHashCode	Serves as the default hash function. (Inherited from Object.)
	GetKey	Gets the key at the specified index of a SortedList object.
	GetKeyList	Gets the keys in a SortedList object.
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	GetValueList	Gets the values in a SortedList object.
	IndexOfKey	Returns the zero-based index of the specified key in a SortedList object.
	IndexOfValue	Returns the zero-based index of the first occurrence of the specified value in a SortedList object.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	Remove	Removes the element with the specified key from a SortedList object.
	RemoveAt	Removes the element at the specified index of a SortedList object.
	SetByIndex	Replaces the value at a specific index in a SortedList object.
	Synchronized	Returns a synchronized (thread-safe) wrapper for a SortedList object.
	ToString	Returns a string that represents the current object. (Inherited from Object.)
	TrimToSize	Sets the capacity to the actual number of elements in a SortedList object.

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Extension Methods

Show:  Inherited  Protected

	Name	Description
	AsParallel	Enables parallelization of a query. (Defined by ParallelEnumerable.)
	AsQueryable	Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
	Cast<TResult>	Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
	OfType<TResult>	Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)

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Explicit Interface Implementations

Show:  Inherited  Protected

	Name	Description
	IEnumerable.GetEnumerator	Returns an IEnumerator that iterates through the SortedList.

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Remarks

For the generic version of this collection, see System.Collections.Generic.SortedList<TKey, TValue>.

A SortedList element can be accessed by its key, like an element in any IDictionary implementation, or by its index, like an element in any IList implementation.

A SortedList object internally maintains two arrays to store the elements of the list; that is, one array for the keys and another array for the associated values. Each element is a key/value pair that can be accessed as a DictionaryEntryobject. A key cannot be null, but a value can be.

The capacity of a SortedList object is the number of elements the SortedList can hold. As elements are added to a SortedList, the capacity is automatically increased as required through reallocation. The capacity can be decreased by calling TrimToSize or by setting the Capacity property explicitly.

For very large SortedList objects, you can increase the maximum capacity to 2 billion elements on a 64-bit system by setting the enabled attribute of the gcAllowVeryLargeObjects configuration element to true in the run-time environment.

The elements of a SortedList object are sorted by the keys either according to a specific IComparer implementation specified when the SortedList is created or according to the IComparable implementation provided by the keys themselves. In either case, a SortedList does not allow duplicate keys.

The index sequence is based on the sort sequence. When an element is added, it is inserted into SortedList in the correct sort order, and the indexing adjusts accordingly. When an element is removed, the indexing also adjusts accordingly. Therefore, the index of a specific key/value pair might change as elements are added or removed from the SortedList object.

Operations on a SortedList object tend to be slower than operations on a Hashtable object because of the sorting. However, the SortedList offers more flexibility by allowing access to the values either through the associated keys or through the indexes.

Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.

The foreach statement of the C# language (for each in Visual Basic) requires the type of each element in the collection. Since each element of the SortedList object is a key/value pair, the element type is not the type of the key or the type of the value. Rather, the element type is DictionaryEntry. For example:

C#

C++

VB

foreach (DictionaryEntry de in mySortedList)
{
    //...
}

The foreach statement is a wrapper around the enumerator, which allows only reading from, not writing to, the collection.

Examples

The following code example shows how to create and initialize a SortedList object and how to print out its keys and values.

C#

C++

VB

using System;
using System.Collections;
public class SamplesSortedList  {

   public static void Main()  {

      // Creates and initializes a new SortedList.
      SortedList mySL = new SortedList();
       mySL.Add("Third", "!");
       mySL.Add("Second", "World");
       mySL.Add("First", "Hello");

      // Displays the properties and values of the SortedList.
      Console.WriteLine( "mySL" );
      Console.WriteLine( "  Count:    {0}", mySL.Count );
      Console.WriteLine( "  Capacity: {0}", mySL.Capacity );
      Console.WriteLine( "  Keys and Values:" );
      PrintKeysAndValues( mySL );
   }


   public static void PrintKeysAndValues( SortedList myList )  {
      Console.WriteLine( "\t-KEY-\t-VALUE-" );
      for ( int i = 0; i < myList.Count; i++ )  {
         Console.WriteLine( "\t{0}:\t{1}", myList.GetKey(i), myList.GetByIndex(i) );
      }
      Console.WriteLine();
   }
}
/*
This code produces the following output.

mySL
  Count:    3
  Capacity: 16
  Keys and Values:
    -KEY-    -VALUE-
    First:    Hello
    Second:    World
    Third:    !
*/

Version Information

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Platforms

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Thread Safety

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

A SortedList object can support multiple readers concurrently, as long as the collection is not modified. To guarantee the thread safety of the SortedList, all operations must be done through the wrapper returned by the Synchronizedmethod.

Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

See Also

Reference

System.Collections Namespace

IComparable

IComparer

IDictionary

Hashtable

System.Collections.Generic .SortedList <TKey, TValue >

Other Resources

Performing Culture-Insensitive String Operations in Collections