List.IndexOf Method (T, Int32)

public int IndexOf (
	T item,
	int index
)

public int IndexOf (
	T item, 
	int index
)

public function IndexOf (
	item : T, 
	index : int
) : int

Not applicable.

Parameters

item

The object to locate in the List. The value can be a null reference (Nothing in Visual Basic) for reference types.

index

The zero-based starting index of the search.

Return Value

The List is searched forward starting at index and ending at the last element.

This method determines equality using the default equality comparer EqualityComparer.Default for T, the type of values in the list.

This method performs a linear search; therefore, this method is an O(n) operation, where n is the number of elements from index to the end of the List.

The following code example demonstrates all three overloads of the IndexOf method. A List of strings is created, with one entry that appears twice, at index location 0 and index location 5. The IndexOf(T) method overload searches the list from the beginning, and finds the first occurrence of the string. The IndexOf(T,Int32) method overload is used to search the list beginning with index location 3 and continuing to the end of the list, and finds the second occurrence of the string. Finally, the IndexOf(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.

using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        List<string> dinosaurs = new List<string>();

        dinosaurs.Add("Tyrannosaurus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("Mamenchisaurus");
        dinosaurs.Add("Brachiosaurus");
        dinosaurs.Add("Deinonychus");
        dinosaurs.Add("Tyrannosaurus");
        dinosaurs.Add("Compsognathus");

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

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

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

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

/* This code example produces the following output:

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Brachiosaurus
Deinonychus
Tyrannosaurus
Compsognathus

IndexOf("Tyrannosaurus"): 0

IndexOf("Tyrannosaurus", 3): 5

IndexOf("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

.NET Compact Framework

XNA Framework