Array.FindIndex Method
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Searches for an element that matches the conditions defined by a specified predicate, and returns the zero-based index of the first occurrence within an Array or a portion of it.
FindIndex<T>(T[], Predicate<T>) |
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. |
FindIndex<T>(T[], Int32, Predicate<T>) |
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. |
FindIndex<T>(T[], Int32, Int32, Predicate<T>) |
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 starts at the specified index and contains the specified number of elements. |
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>(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.
Note
In C#, F#, 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>(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>(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;
}
else
{
return false;
}
};
void main()
{
array<String^>^ dinosaurs = { "Compsognathus",
"Amargasaurus", "Oviraptor", "Velociraptor",
"Deinonychus", "Dilophosaurus", "Gallimimus",
"Triceratops" };
Console::WriteLine();
for each(String^ dinosaur in dinosaurs )
{
Console::WriteLine(dinosaur);
}
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:
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
*/
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
*/
open System
// Search predicate returns true if a string ends in "saurus".
let endsWithSaurus (s: string) =
s.Length > 5 && s.Substring(s.Length - 6).ToLower() = "saurus"
let dinosaurs =
[| "Compsognathus"; "Amargasaurus"
"Oviraptor"; "Velociraptor"
"Deinonychus"; "Dilophosaurus"
"Gallimimus"; "Triceratops" |]
printfn ""
for dino in dinosaurs do
printfn $"{dino}"
Array.FindIndex(dinosaurs, endsWithSaurus)
|> printfn "\nArray.FindIndex(dinosaurs, EndsWithSaurus): %i"
Array.FindIndex(dinosaurs, 2, endsWithSaurus)
|> printfn "\nArray.FindIndex(dinosaurs, 2, EndsWithSaurus): %i"
Array.FindIndex(dinosaurs, 2, 3, endsWithSaurus)
|> printfn "\nArray.FindIndex(dinosaurs, 2, 3, EndsWithSaurus): %i"
// 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
Public Class Example
Public Shared Sub Main()
Dim dinosaurs() As String = { "Compsognathus", _
"Amargasaurus", "Oviraptor", "Velociraptor", _
"Deinonychus", "Dilophosaurus", "Gallimimus", _
"Triceratops" }
Console.WriteLine()
For Each dinosaur As String In dinosaurs
Console.WriteLine(dinosaur)
Next
Console.WriteLine(vbLf & _
"Array.FindIndex(dinosaurs, AddressOf EndsWithSaurus): {0}", _
Array.FindIndex(dinosaurs, AddressOf EndsWithSaurus))
Console.WriteLine(vbLf & _
"Array.FindIndex(dinosaurs, 2, AddressOf EndsWithSaurus): {0}", _
Array.FindIndex(dinosaurs, 2, AddressOf EndsWithSaurus))
Console.WriteLine(vbLf & _
"Array.FindIndex(dinosaurs, 2, 3, AddressOf EndsWithSaurus): {0}", _
Array.FindIndex(dinosaurs, 2, 3, AddressOf EndsWithSaurus))
End Sub
' Search predicate returns true if a string ends in "saurus".
Private Shared Function EndsWithSaurus(ByVal s As String) _
As Boolean
' AndAlso prevents evaluation of the second Boolean
' expression if the string is so short that an error
' would occur.
If (s.Length > 5) AndAlso _
(s.Substring(s.Length - 6).ToLower() = "saurus") Then
Return True
Else
Return False
End If
End Function
End Class
' This code example produces the following output:
'
'Compsognathus
'Amargasaurus
'Oviraptor
'Velociraptor
'Deinonychus
'Dilophosaurus
'Gallimimus
'Triceratops
'
'Array.FindIndex(dinosaurs, AddressOf EndsWithSaurus): 1
'
'Array.FindIndex(dinosaurs, 2, AddressOf EndsWithSaurus): 5
'
'Array.FindIndex(dinosaurs, 2, 3, AddressOf EndsWithSaurus): -1
- Source:
- Array.cs
- Source:
- Array.cs
- Source:
- Array.cs
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.
public:
generic <typename T>
static int FindIndex(cli::array <T> ^ array, Predicate<T> ^ match);
public static int FindIndex<T> (T[] array, Predicate<T> match);
static member FindIndex : 'T[] * Predicate<'T> -> int
Public Shared Function FindIndex(Of T) (array As T(), match As Predicate(Of T)) As Integer
Type Parameters
- T
The type of the elements of the array.
Parameters
- array
- T[]
The one-dimensional, zero-based Array to search.
- match
- Predicate<T>
The Predicate<T> that defines the conditions of the element to search for.
Returns
The zero-based index of the first occurrence of an element that matches the conditions defined by match
, if found; otherwise, -1.
Exceptions
Remarks
The Array is searched forward starting at the first element 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 Length of array
.
See also
- Exists<T>(T[], Predicate<T>)
- Find<T>(T[], Predicate<T>)
- FindLast<T>(T[], Predicate<T>)
- FindAll<T>(T[], Predicate<T>)
- BinarySearch
- IndexOf
- LastIndexOf
- Predicate<T>
Applies to
.NET 9 and other versions
Product | Versions |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
UWP | 10.0 |
- Source:
- Array.cs
- Source:
- Array.cs
- Source:
- Array.cs
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.
public:
generic <typename T>
static int FindIndex(cli::array <T> ^ array, int startIndex, Predicate<T> ^ match);
public static int FindIndex<T> (T[] array, int startIndex, Predicate<T> match);
static member FindIndex : 'T[] * int * Predicate<'T> -> int
Public Shared Function FindIndex(Of T) (array As T(), startIndex As Integer, match As Predicate(Of T)) As Integer
Type Parameters
- T
The type of the elements of the array.
Parameters
- array
- T[]
The one-dimensional, zero-based Array to search.
- startIndex
- Int32
The zero-based starting index of the search.
- match
- Predicate<T>
The Predicate<T> that defines the conditions of the element to search for.
Returns
The zero-based index of the first occurrence of an element that matches the conditions defined by match
, if found; otherwise, -1.
Exceptions
startIndex
is outside the range of valid indexes for array
.
Remarks
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
.
See also
- Exists<T>(T[], Predicate<T>)
- Find<T>(T[], Predicate<T>)
- FindLast<T>(T[], Predicate<T>)
- FindAll<T>(T[], Predicate<T>)
- BinarySearch
- IndexOf
- LastIndexOf
- Predicate<T>
Applies to
.NET 9 and other versions
Product | Versions |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
UWP | 10.0 |
- Source:
- Array.cs
- Source:
- Array.cs
- Source:
- Array.cs
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 starts at the specified index and contains the specified number of elements.
public:
generic <typename T>
static int FindIndex(cli::array <T> ^ array, int startIndex, int count, Predicate<T> ^ match);
public static int FindIndex<T> (T[] array, int startIndex, int count, Predicate<T> match);
static member FindIndex : 'T[] * int * int * Predicate<'T> -> int
Public Shared Function FindIndex(Of T) (array As T(), startIndex As Integer, count As Integer, match As Predicate(Of T)) As Integer
Type Parameters
- T
The type of the elements of the array.
Parameters
- array
- T[]
The one-dimensional, zero-based Array to search.
- startIndex
- Int32
The zero-based starting index of the search.
- count
- Int32
The number of elements in the section to search.
- match
- Predicate<T>
The Predicate<T> that defines the conditions of the element to search for.
Returns
The zero-based index of the first occurrence of an element that matches the conditions defined by match
, if found; otherwise, -1.
Exceptions
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
.
Remarks
The Array is searched forward starting at startIndex
and ending at startIndex
plus count
minus 1, if count
is greater than 0.
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 count
.
See also
- Exists<T>(T[], Predicate<T>)
- Find<T>(T[], Predicate<T>)
- FindLast<T>(T[], Predicate<T>)
- FindAll<T>(T[], Predicate<T>)
- BinarySearch
- IndexOf
- LastIndexOf
- Predicate<T>
Applies to
.NET 9 and other versions
Product | Versions |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1 |
UWP | 10.0 |
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