Contains Method

List(Of T).Contains Method

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Determines whether an element is in the List(Of T).

Namespace:  System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Function Contains ( _
	item As T _
) As Boolean

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.Boolean
true if item is found in the List(Of T); otherwise, false.

Implements

ICollection(Of T).Contains(T)

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, this method is an O(n) operation, where n is Count.

The following code example demonstrates the Contains method and various other properties and methods of the List(Of T) generic class. After the list has been populated, the Contains method is used to search for an item.


Imports System.Collections.Generic

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      Dim dinosaurs As New List(Of String)

      outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf

      dinosaurs.Add("Tyrannosaurus")
      dinosaurs.Add("Amargasaurus")
      dinosaurs.Add("Mamenchisaurus")
      dinosaurs.Add("Deinonychus")
      dinosaurs.Add("Compsognathus")

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf
      outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf

      outputBlock.Text &= vbLf & String.Format("Contains(""Deinonychus"": {0}", _
          dinosaurs.Contains("Deinonychus")) & vbCrLf

      outputBlock.Text &= String.Format(vbLf & "Insert(2, ""Compsognathus"")") & vbCrLf
      dinosaurs.Insert(2, "Compsognathus")

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      outputBlock.Text &= String.Format(vbLf & "dinosaurs(3): {0}", dinosaurs(3)) & vbCrLf

      outputBlock.Text &= vbLf & "Remove(""Compsognathus"")" & vbCrLf
      dinosaurs.Remove("Compsognathus")

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In dinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      dinosaurs.TrimExcess()
      outputBlock.Text &= vbLf & "TrimExcess()" & vbCrLf
      outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf
      outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf

      dinosaurs.Clear()
      outputBlock.Text &= vbLf & "Clear()" & vbCrLf
      outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf
      outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf
   End Sub
End Class

' This code example produces the following output:
'
'Capacity: 0
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'Capacity: 8
'Count: 5
'
'Contains("Deinonychus"): True
'
'Insert(2, "Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Compsognathus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'dinosaurs(3): Mamenchisaurus
'
'Remove("Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'TrimExcess()
'Capacity: 5
'Count: 5
'
'Clear()
'Capacity: 5
'Count: 0


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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