Searches for the specified object and returns the zero-based index of the first occurrence within the range of elements in the ListT that extends from the specified index to the last element.
Assembly: mscorlib (in mscorlib.dll)
Public Function IndexOf ( _
item As T, _
index As [%$TOPIC/s8t42k5w_en-us_VS_110_2_0_0_0_0%] _
) As [%$TOPIC/s8t42k5w_en-us_VS_110_2_0_0_0_1%]public [%$TOPIC/s8t42k5w_en-us_VS_110_2_0_1_0_0%] IndexOf(
T item,
[%$TOPIC/s8t42k5w_en-us_VS_110_2_0_1_0_1%] index
)public:
[%$TOPIC/s8t42k5w_en-us_VS_110_2_0_2_0_0%] IndexOf(
T item,
[%$TOPIC/s8t42k5w_en-us_VS_110_2_0_2_0_1%] index
)member IndexOf :
item:'T *
index:[%$TOPIC/s8t42k5w_en-us_VS_110_2_0_3_0_0%] -> [%$TOPIC/s8t42k5w_en-us_VS_110_2_0_3_0_1%]Parameters
- index
- Type:
SystemInt32
The zero-based starting index of the search. 0 (zero) is valid in an empty list.
Return Value
Type: SystemInt32The zero-based index of the first occurrence of item within the range of elements in the ListT that extends from index to the last element, if found; otherwise, –1.
| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | index is outside the range of valid indexes for the ListT. |
The ListT is searched forward starting at index and ending at the last element.
This method determines equality using the default equality comparer EqualityComparerTDefault 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 the number of elements from index to the end of the ListT.
The following code example demonstrates all three overloads of the IndexOf method. A ListT 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): -1using System;
using System.Collections.Generic;
public class Example
{
public static void Main()
{
List<string> dinosaurs = new List<string>();
dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Mamenchisaurus");
dinosaurs.Add("Brachiosaurus");
dinosaurs.Add("Deinonychus");
dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Compsognathus");
Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
Console.WriteLine(dinosaur);
}
Console.WriteLine("\nIndexOf(\"Tyrannosaurus\"): {0}",
dinosaurs.IndexOf("Tyrannosaurus"));
Console.WriteLine("\nIndexOf(\"Tyrannosaurus\", 3): {0}",
dinosaurs.IndexOf("Tyrannosaurus", 3));
Console.WriteLine("\nIndexOf(\"Tyrannosaurus\", 2, 2): {0}",
dinosaurs.IndexOf("Tyrannosaurus", 2, 2));
}
}
/* 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
*/using namespace System;
using namespace System::Collections::Generic;
void main()
{
List<String^>^ dinosaurs = gcnew List<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(String^ dinosaur in dinosaurs )
{
Console::WriteLine(dinosaur);
}
Console::WriteLine("\nIndexOf(\"Tyrannosaurus\"): {0}",
dinosaurs->IndexOf("Tyrannosaurus"));
Console::WriteLine("\nIndexOf(\"Tyrannosaurus\", 3): {0}",
dinosaurs->IndexOf("Tyrannosaurus", 3));
Console::WriteLine("\nIndexOf(\"Tyrannosaurus\", 2, 2): {0}",
dinosaurs->IndexOf("Tyrannosaurus", 2, 2));
}
/* 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 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
