Array::FindIndex<T> Method (array<T>^, Int32, Predicate<T>^)


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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 range of elements in the Array that extends from the specified index to the last element.

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

generic<typename T>
static int FindIndex(
	array<T>^ array,
	int startIndex,
	Predicate<T>^ match


Type: array<T>^

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

Type: System::Int32

The zero-based starting index of the search.

Type: System::Predicate<T>^

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

Return Value

Type: System::Int32

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

Type Parameters


The type of the elements of the array.

Exception Condition

array is null.


match is null.


startIndex is outside the range of valid indexes for array.

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

The Predicate<T> 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<T>.

This method is an O(n) operation, where n is the number of elements from startIndex to the end 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<T>(array<T>^, Predicate<T>^) 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.


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<T>(array<T>^, Int32, Predicate<T>^) 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<T>(array<T>^, Int32, Int32, Predicate<T>^) 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 namespace System;

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

void main()
    array<String^>^ dinosaurs = { "Compsognathus", 
        "Amargasaurus",   "Oviraptor",      "Velociraptor", 
        "Deinonychus",    "Dilophosaurus",  "Gallimimus", 
        "Triceratops" };

    for each(String^ dinosaur in dinosaurs )

    Console::WriteLine("\nArray::FindIndex(dinosaurs, EndsWithSaurus): {0}", 
        Array::FindIndex(dinosaurs, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindIndex(dinosaurs, 2, EndsWithSaurus): {0}",
        Array::FindIndex(dinosaurs, 2, gcnew Predicate<String^>(EndsWithSaurus)));

    Console::WriteLine("\nArray::FindIndex(dinosaurs, 2, 3, EndsWithSaurus): {0}",
        Array::FindIndex(dinosaurs, 2, 3, gcnew Predicate<String^>(EndsWithSaurus)));

/* This code example produces the following output:


Array::FindIndex(dinosaurs, EndsWithSaurus): 1

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

Array::FindIndex(dinosaurs, 2, 3, EndsWithSaurus): -1

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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