Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

Array.FindIndex Generic Method (T[], Generic Predicate)

Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the first occurrence within the entire Array.

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

public static int FindIndex<T> (
	T[] array,
	Predicate<T> match
)
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.

match

The Predicate that defines the conditions of the element to search for.

Return Value

The zero-based index of the first occurrence of an element that matches the conditions defined by match, if found; otherwise, –1.

Exception typeCondition

ArgumentNullException

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

-or-

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

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

The Predicate is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of array are individually passed to the Predicate.

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

The following code example demonstrates all three overloads of the FindIndex generic method. An array of strings is created, containing 8 dinosaur names, two of which (at positions 1 and 5) end with "saurus". The code example also defines a search predicate method named EndsWithSaurus, which accepts a string parameter and returns a Boolean value indicating whether the input string ends in "saurus".

The FindIndex(J[],Generic Predicate) method overload traverses the array from the beginning, passing each element in turn to the EndsWithSaurus method. The search stops when the EndsWithSaurus method returns true for the element at position 1.

NoteNote:

In C# and Visual Basic, it is not necessary to create the Predicate<string> delegate (Predicate(Of String) in Visual Basic) explicitly. These languages infer the correct delegate from context and create it automatically.

The FindIndex(J[],Int32,Generic Predicate) method overload is used to search the array beginning at position 2 and continuing to the end of the array. It finds the element at position 5. Finally, the FindIndex(J[],Int32,Int32,Generic Predicate) method overload is used to search the range of three elements beginning at position 2. It returns –1 because there are no dinosaur names in that range that end with "saurus".

using System;

public class Example
{
    public static void Main()
    {
        string[] dinosaurs = { "Compsognathus", 
            "Amargasaurus",   "Oviraptor",      "Velociraptor", 
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
            "Triceratops" };

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

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

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

        Console.WriteLine(
            "\nArray.FindIndex(dinosaurs, 2, 3, EndsWithSaurus): {0}",
            Array.FindIndex(dinosaurs, 2, 3, EndsWithSaurus));
    }

    // Search predicate returns true if a string ends in "saurus".
    private static bool EndsWithSaurus(String s)
    {
        if ((s.Length > 5) && 
            (s.Substring(s.Length - 6).ToLower() == "saurus"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.FindIndex(dinosaurs, EndsWithSaurus): 1

Array.FindIndex(dinosaurs, 2, EndsWithSaurus): 5

Array.FindIndex(dinosaurs, 2, 3, EndsWithSaurus): -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
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

Show:
© 2014 Microsoft