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Array.IndexOf Generic Method (T[], T, Int32, Int32)

Searches for the specified object and returns the index of the first occurrence within the range of elements in the Array that starts at the specified index and contains the specified number of elements.

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

'Declaration
Public Shared Function IndexOf(Of T) ( _
	array As T(), _
	value As T, _
	startIndex As Integer, _
	count As Integer _
) As Integer
'Usage
Dim array As T()
Dim value As T
Dim startIndex As Integer
Dim count As Integer
Dim returnValue As Integer

returnValue = Array.IndexOf(array, value, startIndex, count)
J# supports the use of generic types and methods, but not the declaration of new ones.
JScript does not support generic types and methods.
Not applicable.

Type Parameters

T

The type of the elements of the array.

Parameters

array

The one-dimensional, zero-based Array to search.

value

The object to locate in array.

startIndex

The zero-based starting index of the search.

count

The number of elements in the section to search.

Return Value

The zero-based index of the first occurrence of value within the range of elements in array that starts at startIndex and contains the number of elements specified in count, if found; otherwise, –1.

Exception typeCondition

ArgumentNullException

array is a null reference (Nothing in Visual Basic).

ArgumentOutOfRangeException

startIndex is outside the range of valid indexes for array.

-or-

count is less than zero.

-or-

startIndex and count do not specify a valid section in array.

The Array is searched forward starting at startIndex and ending at startIndex plus count minus 1, if count is greater than 0.

The elements are compared to the specified value using the Object.Equals method. If the element type is a nonintrinsic (user-defined) type, the Equals implementation of that type is used.

Passing the Length property of the array as the startindex parameter results in a return value of -1; passing values greater than Length raises an ArgumentOutOfRangeException.

This method is an O(n) operation, where n is count.

The following code example demonstrates all three generic overloads of the IndexOf method. An array of strings is created, with one entry that appears twice, at index location 0 and index location 5. The IndexOf(J[],J) method overload searches the array from the beginning, and finds the first occurrence of the string. The IndexOf(J[],J,Int32) method overload is used to search the array beginning with index location 3 and continuing to the end of the array, and finds the second occurrence of the string. Finally, the IndexOf(J[],J,Int32,Int32) method overload is used to search a range of two entries, beginning at index location two; it returns –1 because there are no instances of the search string in that range.

Imports System

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs() As String = { "Tyrannosaurus", _
            "Amargasaurus", _
            "Mamenchisaurus", _
            "Brachiosaurus", _
            "Deinonychus", _
            "Tyrannosaurus", _
            "Compsognathus" }

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & _
            "Array.IndexOf(dinosaurs, ""Tyrannosaurus""): {0}", _
            Array.IndexOf(dinosaurs, "Tyrannosaurus"))

        Console.WriteLine(vbLf & _
            "Array.IndexOf(dinosaurs, ""Tyrannosaurus"", 3): {0}", _
            Array.IndexOf(dinosaurs, "Tyrannosaurus", 3))

        Console.WriteLine(vbLf & _
            "Array.IndexOf(dinosaurs, ""Tyrannosaurus"", 2, 2): {0}", _
            Array.IndexOf(dinosaurs, "Tyrannosaurus", 2, 2))

    End Sub
End Class

' This code example produces the following output:
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Brachiosaurus
'Deinonychus
'Tyrannosaurus
'Compsognathus
'
'Array.IndexOf(dinosaurs, "Tyrannosaurus"): 0
'
'Array.IndexOf(dinosaurs, "Tyrannosaurus", 3): 5
'
'Array.IndexOf(dinosaurs, "Tyrannosaurus", 2, 2): -1

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0

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