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Array.TrueForAll Generic Method

Note: This method is new in the .NET Framework version 2.0.

Determines whether every element in the array matches the conditions defined by the specified predicate.

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

'Declaration
Public Shared Function TrueForAll(Of T) ( _
	array As T(), _
	match As Predicate(Of T) _
) As Boolean
'Usage
Dim array As T()
Dim match As Predicate(Of T)
Dim returnValue As Boolean

returnValue = Array.TrueForAll(array, match)
J# supports the use of generic types and methods, but not the declaration of new ones.
JScript does not support generic types and methods.

Type Parameters

T

The type of the elements of the array.

Parameters

array

The one-dimensional, zero-based Array to check against the conditions

match

The Predicate that defines the conditions to check against the elements.

Return Value

true if every element in array matches the conditions defined by the specified predicate; otherwise, false. If there are no elements in the array, the return value is true.

Exception typeCondition

ArgumentNullException

array is a null reference (Nothing in Visual Basic).

-or-

match is a null reference (Nothing in Visual Basic).

The Predicate is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of array are individually passed to the Predicate, and processing is stopped when the delegate returns false for any element.

This method is an O(n) operation, where n is the Length of array.

The following code example demonstrates the TrueForAll generic method and several other generic methods that use the Predicate generic delegate.

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 Exists method stops and returns true at the first element for which the predicate method returns true, which in this case is "Amargasaurus".

NoteNote

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 TrueForAll method stops and returns false at the first element for which the predicate method returns false.

The Find method traverses the array from the beginning, passing each element in turn to the EndsWithSaurus method. The search stops when the EndsWithSaurus method returns true for the element "Amargasaurus".

The FindLast method is used to search the array backward from the end. It finds the element "Dilophosaurus" at position 5. The FindAll method is used to return an array containing all the elements that end in "saurus". The elements are displayed.

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.Exists(dinosaurs, AddressOf EndsWithSaurus): {0}", _
            Array.Exists(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.TrueForAll(dinosaurs, AddressOf EndsWithSaurus: {0}", _
            Array.TrueForAll(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.Find(dinosaurs, AddressOf EndsWithSaurus): {0}", _
            Array.Find(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLast(dinosaurs, AddressOf EndsWithSaurus): {0}", _
            Array.FindLast(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindAll(dinosaurs, AddressOf EndsWithSaurus):")
        Dim subArray() As String = _
            Array.FindAll(dinosaurs, AddressOf EndsWithSaurus)

        For Each dinosaur As String In subArray
            Console.WriteLine(dinosaur)
        Next
        
    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.Exists(dinosaurs, AddressOf EndsWithSaurus): True
'
'Array.TrueForAll(dinosaurs, AddressOf EndsWithSaurus: False
'
'Array.Find(dinosaurs, AddressOf EndsWithSaurus): Amargasaurus
'
'Array.FindLast(dinosaurs, AddressOf EndsWithSaurus): Dilophosaurus
'
'Array.FindAll(dinosaurs, AddressOf EndsWithSaurus):
'Amargasaurus
'Dilophosaurus

Windows 98, Windows 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 .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

.NET Compact Framework

Supported in: 2.0

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