Collection(Of T).IndexOf Method
Searches for the specified object and returns the zero-based index of the first occurrence within the entire Collection(Of T).
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Function IndexOf ( _ item As T _ ) As Integer 'Usage Dim instance As Collection Dim item As T Dim returnValue As Integer returnValue = instance.IndexOf(item)
Parameters
- item
- Type: T
The object to locate in the List(Of T). The value can be Nothing for reference types.
Return Value
Type: System.Int32The zero-based index of the first occurrence of item within the entire Collection(Of T), if found; otherwise, -1.
Implements
IList(Of T).IndexOf(T)The Collection(Of T) is searched forward starting at the first element and ending at the last element.
This method determines equality using the default equality comparer EqualityComparer(Of T).Default for T, the type of values in the list.
This method performs a linear search; therefore, the average execution time is proportional to Count. That is, this method is an O(n) operation, where n is Count.
The following code example demonstrates many of the properties and methods of Collection(Of T). The code example creates a collection of strings, uses the Add method to add several strings, displays the Count, and lists the strings. The example uses the IndexOf method to find the index of a string and the Contains method to determine whether a string is in the collection. The example inserts a string using the Insert method and retrieves and sets strings using the default Item property (the indexer in C#). The example removes strings by string identity using the Remove method and by index using the RemoveAt method. Finally, the Clear method is used to clear all strings from the collection.
Imports System Imports System.Collections.Generic Imports System.Collections.ObjectModel Public Class Demo Public Shared Sub Main() Dim dinosaurs As New Collection(Of String) dinosaurs.Add("Psitticosaurus") dinosaurs.Add("Caudipteryx") dinosaurs.Add("Compsognathus") dinosaurs.Add("Muttaburrasaurus") Console.WriteLine("{0} dinosaurs:", dinosaurs.Count) Display(dinosaurs) Console.WriteLine(vbLf & "IndexOf(""Muttaburrasaurus""): {0}", _ dinosaurs.IndexOf("Muttaburrasaurus")) Console.WriteLine(vbLf & "Contains(""Caudipteryx""): {0}", _ dinosaurs.Contains("Caudipteryx")) Console.WriteLine(vbLf & "Insert(2, ""Nanotyrannus"")") dinosaurs.Insert(2, "Nanotyrannus") Display(dinosaurs) Console.WriteLine(vbLf & "dinosaurs(2): {0}", dinosaurs(2)) Console.WriteLine(vbLf & "dinosaurs(2) = ""Microraptor""") dinosaurs(2) = "Microraptor" Display(dinosaurs) Console.WriteLine(vbLf & "Remove(""Microraptor"")") dinosaurs.Remove("Microraptor") Display(dinosaurs) Console.WriteLine(vbLf & "RemoveAt(0)") dinosaurs.RemoveAt(0) Display(dinosaurs) Console.WriteLine(vbLf & "dinosaurs.Clear()") dinosaurs.Clear() Console.WriteLine("Count: {0}", dinosaurs.Count) End Sub Private Shared Sub Display(ByVal cs As Collection(Of String)) Console.WriteLine() For Each item As String In cs Console.WriteLine(item) Next item End Sub End Class ' This code example produces the following output: ' '4 dinosaurs: ' 'Psitticosaurus 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'IndexOf("Muttaburrasaurus"): 3 ' 'Contains("Caudipteryx"): True ' 'Insert(2, "Nanotyrannus") ' 'Psitticosaurus 'Caudipteryx 'Nanotyrannus 'Compsognathus 'Muttaburrasaurus ' 'dinosaurs(2): Nanotyrannus ' 'dinosaurs(2) = "Microraptor" ' 'Psitticosaurus 'Caudipteryx 'Microraptor 'Compsognathus 'Muttaburrasaurus ' 'Remove("Microraptor") ' 'Psitticosaurus 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'RemoveAt(0) ' 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'dinosaurs.Clear() 'Count: 0
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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.