Array.IndexOf(T) Method (T[], T) (System)

IndexOf(T) Method (T[], T)

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

Array..::.IndexOf<(Of <(T>)>) Method (array<T>[]()[], T)

Updated: November 2007

Searches for the specified object and returns the index of the first occurrence within the entire Array.

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

Syntax

Visual Basic (Declaration)

Public Shared Function IndexOf(Of T) ( _
    array As T(), _
    value As T _
) As Integer

Visual Basic (Usage)

Dim array As T()
Dim value As T
Dim returnValue As Integer

returnValue = Array.IndexOf(array, _
    value)

public static int IndexOf<T>(
    T[] array,
    T value
)

Visual C++

public:
generic<typename T>
static int IndexOf(
    array<T>^ array, 
    T value
)

J# supports the use of generic APIs, but not the declaration of new ones.

JScript

JScript does not support generic types or methods.

Type Parameters

T: The type of the elements of the array.

Parameters

array: Type: array<T>[]()[]
The one-dimensional, zero-based Array to search.

value: Type: T
The object to locate in array.

Return Value

Type: System..::.Int32

The zero-based index of the first occurrence of value within the entire array, if found; otherwise, –1.

Exceptions

Exception	Condition
ArgumentNullException	array is nullNothingnullptra null reference (Nothing in Visual Basic).

Remarks

The Array is searched forward starting at the first element and ending at the last element.

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.

This method is an O(n) operation, where n is the Length of array.

Examples

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<(Of <(T>)>)(array<T>[]()[], T) method overload searches the array from the beginning, and finds the first occurrence of the string. The IndexOf<(Of <(T>)>)(array<T>[]()[], T, 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<(Of <(T>)>)(array<T>[]()[], T, 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.

Visual Basic

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

using System;

public class Example
{
    public static void Main()
    {
        string[] dinosaurs = { "Tyrannosaurus",
            "Amargasaurus",
            "Mamenchisaurus",
            "Brachiosaurus",
            "Deinonychus",
            "Tyrannosaurus",
            "Compsognathus" };

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine(
            "\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\"): {0}", 
            Array.IndexOf(dinosaurs, "Tyrannosaurus"));

        Console.WriteLine(
            "\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\", 3): {0}", 
            Array.IndexOf(dinosaurs, "Tyrannosaurus", 3));

        Console.WriteLine(
            "\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\", 2, 2): {0}", 
            Array.IndexOf(dinosaurs, "Tyrannosaurus", 2, 2));
    }
}

/* 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
 */

Visual C++

using namespace System;

void main()
{
    array<String^>^ dinosaurs = { "Tyrannosaurus", 
        "Amargasaurus",
        "Mamenchisaurus",
        "Brachiosaurus",
        "Deinonychus",
        "Tyrannosaurus",
        "Compsognathus" };

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\"): {0}", 
        Array::IndexOf(dinosaurs, "Tyrannosaurus"));

    Console::WriteLine("\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\", 3): {0}", 
        Array::IndexOf(dinosaurs, "Tyrannosaurus", 3));

    Console::WriteLine("\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\", 2, 2): {0}", 
        Array::IndexOf(dinosaurs, "Tyrannosaurus", 2, 2));
}

/* 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
 */

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, 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

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.

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