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.
(in mscorlib.dll)
Visual Basic (Declaration)
Public Shared Function FindIndex(Of T) ( _
array As T(), _
match As Predicate(Of T) _
) As Integer
Dim array As T()
Dim match As Predicate(Of T)
Dim returnValue As Integer
returnValue = Array.FindIndex(array, _
match)
public static int FindIndex<T>(
T[] array,
Predicate<T> match
)
public:
generic<typename T>
static int FindIndex(
array<T>^ array,
Predicate<T>^ match
)
JScript does not support generic types or methods.
Type Parameters
- T
The type of the elements of the array.
Return Value
Type:
System..::.Int32The zero-based index of the first occurrence of an element that matches the conditions defined by match, if found; otherwise, –1.
| Exception | Condition |
|---|
| ArgumentNullException |
array is nullNothingnullptra null reference (Nothing in Visual Basic). -or-
match is nullNothingnullptra null reference (Nothing in Visual Basic). |
The Array is searched forward starting at the first element and ending at the last element.
The Predicate<(Of <(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<(Of <(T>)>).
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<(Of <(T>)>)(array<T>[]()[], Predicate<(Of <(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.
.gif) Note: |
|---|
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<(Of <(T>)>)(array<T>[]()[], Int32, Predicate<(Of <(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<(Of <(T>)>)(array<T>[]()[], Int32, Int32, Predicate<(Of <(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".
Imports System
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
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
*/
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
*/
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
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.
.NET Framework
Supported in: 3.5, 3.0, 2.0
Reference