Searches for the specified object and returns the zero-based index of the first occurrence within the entire
List.
Namespace: System.Collections.Generic
Assembly: mscorlib (in mscorlib.dll)
'Usage
Dim instance As List(Of T)
Dim item As T
Dim returnValue As Integer
returnValue = instance.IndexOf(item)
'Declaration
Public Function IndexOf ( _
item As T _
) As Integer
public final int IndexOf (
T item
)
Parameters
- item
The object to locate in the List. The value can be a null reference (Nothing in Visual Basic) for reference types.
Return Value
The zero-based index of the first occurrence of item within the entire List, if found; otherwise, –1.
The List is searched forward starting at the first element and ending at the last element.
This method determines equality using the default equality comparer EqualityComparer.Default for T, the type of values in the list.
This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.
The following code example demonstrates all three overloads of the IndexOf method. A List of strings is created, with one entry that appears twice, at index location 0 and index location 5. The IndexOf(T) method overload searches the list from the beginning, and finds the first occurrence of the string. The IndexOf(T,Int32) method overload is used to search the list beginning with index location 3 and continuing to the end of the list, and finds the second occurrence of the string. Finally, the IndexOf(T,Int32,Int32) method overload is used to search a range of two entries, beginning at index location two; it returns –1 because there are no instances of the search string in that range.
Imports System
Imports System.Collections.Generic
Public Class Example
Public Shared Sub Main()
Dim dinosaurs As New List(Of String)
dinosaurs.Add("Tyrannosaurus")
dinosaurs.Add("Amargasaurus")
dinosaurs.Add("Mamenchisaurus")
dinosaurs.Add("Brachiosaurus")
dinosaurs.Add("Deinonychus")
dinosaurs.Add("Tyrannosaurus")
dinosaurs.Add("Compsognathus")
Console.WriteLine()
For Each dinosaur As String In dinosaurs
Console.WriteLine(dinosaur)
Next
Console.WriteLine(vbLf & _
"IndexOf(""Tyrannosaurus""): {0}", _
dinosaurs.IndexOf("Tyrannosaurus"))
Console.WriteLine(vbLf & _
"IndexOf(""Tyrannosaurus"", 3): {0}", _
dinosaurs.IndexOf("Tyrannosaurus", 3))
Console.WriteLine(vbLf & _
"IndexOf(""Tyrannosaurus"", 2, 2): {0}", _
dinosaurs.IndexOf("Tyrannosaurus", 2, 2))
End Sub
End Class
' This code example produces the following output:
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Brachiosaurus
'Deinonychus
'Tyrannosaurus
'Compsognathus
'
'IndexOf("Tyrannosaurus"): 0
'
'IndexOf("Tyrannosaurus", 3): 5
'
'IndexOf("Tyrannosaurus", 2, 2): -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
.NET Compact Framework
Supported in: 2.0
XNA Framework
Supported in: 1.0