SortedList.Add Method (Object, Object)


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Adds an element with the specified key and value to a SortedList object.

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

public virtual void Add(
	object key,
	object value


Type: System.Object

The key of the element to add.

Type: System.Object

The value of the element to add. The value can be null.

Exception Condition

key is null.


An element with the specified key already exists in the SortedList object.


The SortedList is set to use the IComparable interface, and key does not implement the IComparable interface.


The SortedList is read-only.


The SortedList has a fixed size.


There is not enough available memory to add the element to the SortedList.


The comparer throws an exception.

The insertion point is determined based on the comparer selected, either explicitly or by default, when the SortedList object was created.

If Count already equals Capacity, the capacity of the SortedList object is increased by automatically reallocating the internal array, and the existing elements are copied to the new array before the new element is added.

You can also use the Item property to add new elements by setting the value of a key that does not exist in the SortedList object (for example, myCollection["myNonexistentKey"] = myValue). However, if the specified key already exists in the SortedList, setting the Item property overwrites the old value. In contrast, the Add method does not modify existing elements.

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.

A key cannot be null, but a value can be.

This method is an O(n) operation for unsorted data, where n is Count. It is an O(log n) operation if the new element is added at the end of the list. If insertion causes a resize, the operation is O(n).

The following code example shows how to add elements to a SortedList object.

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

   public static void Main()  {

      // Creates and initializes a new SortedList.
      SortedList mySL = new SortedList();
      mySL.Add( "one", "The" );
      mySL.Add( "two", "quick" );
      mySL.Add( "three", "brown" );
      mySL.Add( "four", "fox" );

      // Displays the SortedList.
      Console.WriteLine( "The SortedList contains the following:" );
      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) );
This code produces the following output.

The SortedList contains the following:
    -KEY-    -VALUE-
    four:    fox
    one:    The
    three:    brown
    two:    quick

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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