SortedList.IndexOfKey Method (Object)


Returns the zero-based index of the specified key in a SortedList object.

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

Public Overridable Function IndexOfKey (
	key As Object
) As Integer


Type: System.Object

The key to locate in the SortedList object.

Return Value

Type: System.Int32

The zero-based index of the key parameter, if key is found in the SortedList object; otherwise, -1.

Exception Condition

key is null.


The comparer throws an exception.

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.

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.

This method uses a binary search algorithm; therefore, this method is an O(log n) operation, where n is Count.

Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.

The following code example shows how to determine the index of a key or a value in a SortedList object.

Imports System
Imports System.Collections
Imports Microsoft.VisualBasic

Public Class SamplesSortedList    

    Public Shared Sub Main()

        ' Creates and initializes a new SortedList.
        Dim mySL As New SortedList()
        mySL.Add(1, "one")
        mySL.Add(3, "three")
        mySL.Add(2, "two")
        mySL.Add(4, "four")
        mySL.Add(0, "zero")

        ' Displays the values of the SortedList.
        Console.WriteLine("The SortedList contains the " & _
           "following values:")

        ' Searches for a specific key.
        Dim myKey As Integer = 2
        Console.WriteLine("The key ""{0}"" is at index {1}.", myKey, _

        ' Searches for a specific value.
        Dim myValue As String = "three"
        Console.WriteLine("The value ""{0}"" is at index {1}.", myValue, _
    End Sub    

    Public Shared Sub PrintIndexAndKeysAndValues(myList As SortedList)
        Console.WriteLine(ControlChars.Tab & "-INDEX-" & ControlChars.Tab & _
           "-KEY-" & ControlChars.Tab & "-VALUE-")
        Dim i As Integer
        For i = 0 To myList.Count - 1
            Console.WriteLine(ControlChars.Tab & "[{0}]:" & ControlChars.Tab & _
               "{1}" & ControlChars.Tab & "{2}", i, myList.GetKey(i), _
        Next i
    End Sub
End Class

' This code produces the following output.
' The SortedList contains the following values:
'     -INDEX-    -KEY-    -VALUE-
'     [0]:    0    zero
'     [1]:    1    one
'     [2]:    2    two
'     [3]:    3    three
'     [4]:    4    four
' The key "2" is at index 2.
' The value "three" is at index 3.

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