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.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Function FindIndex(Of T) ( _
array As T(), _
startIndex As Integer, _
match As Predicate(Of T) _
) As Integerpublic static int FindIndex<T>(
T[] array,
int startIndex,
Predicate<T> match
)
public:
generic<typename T>
static int FindIndex(
array<T>^ array,
int startIndex,
Predicate<T>^ match
)static member FindIndex :
array:'T[] *
startIndex:int *
match:Predicate<'T> -> int
Type Parameters
- T
The type of the elements of the array.
Parameters
- array
- Type:
array< T> [] () []
The one-dimensional, zero-based Array to search.
- startIndex
- Type: System
. . :: . Int32
The zero-based starting index of the search.
- match
- Type: System
. . :: . Predicate< (Of < ( T> ) > )
The Predicate< (Of < ( T> ) > ) that defines the conditions of the element to search for.
Return Value
Type: SystemThe 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 -or- match is |
| ArgumentOutOfRangeException | 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
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
.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
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 SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.