Array.TrueForAll(T) Method (System)

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.NET Framework Class Library
Array.TrueForAll<T> Method

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

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
Syntax
Visual Basic
Public Shared Function TrueForAll(Of T) ( _
	array As T(), _
	match As Predicate(Of T) _
) As Boolean
C#
public static bool TrueForAll<T>(
	T[] array,
	Predicate<T> match
)
Visual C++
public:
generic<typename T>
static bool TrueForAll(
	array<T>^ array, 
	Predicate<T>^ match
)
F#
static member TrueForAll : 
        array:'T[] * 
        match:Predicate<'T> -> bool

Type Parameters

T

The type of the elements of the array.

Parameters

array
Type: T[]
The one-dimensional, zero-based Array to check against the conditions
match
Type: System.Predicate<T>
The Predicate<T> that defines the conditions to check against the elements.

Return Value

Type: System.Boolean
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.
Exceptions
Exception Condition
ArgumentNullException

array is null.

-or-

match is null.
Remarks

The Predicate<T> 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<T>, 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.

Examples

The following code example demonstrates the TrueForAll<T> generic method and several other generic methods that use the Predicate<T> 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<T> method stops and returns true at the first element for which the predicate method returns true, which in this case is "Amargasaurus".

Note Note

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<T> method stops and returns false at the first element for which the predicate method returns false.

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

Visual Basic

Imports System

Public Class DinoDiscoverySet

    Public Shared Sub Main()
        Dim dinosaurs() As String = { "Compsognathus", _
            "Amargasaurus",   "Oviraptor",      "Velociraptor", _
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", _
            "Triceratops" }

        Dim GoMesozoic As New DinoDiscoverySet(dinosaurs)

        GoMesozoic.DiscoverAll()
        GoMesozoic.DiscoverByEnding("saurus")
    End Sub

    Private dinosaurs As String()

    Public Sub New(items() As String)
        dinosaurs = items
    End Sub

    Public Sub DiscoverAll()
        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next dinosaur
    End Sub

    Public Sub DiscoverByEnding(Ending As String)
        Dim dinoType As Predicate(Of String)

        Select Case Ending.ToLower()
            Case "raptor"
                dinoType = AddressOf EndsWithRaptor
            Case "tops"
                dinoType = AddressOf EndsWithTops
            Case "saurus"
                dinoType = AddressOf EndsWithSaurus
            Case Else
                dinoType = AddressOf EndsWithSaurus
        End Select

        Console.WriteLine(vbNewLine + _
            "Array.Exists(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.Exists(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.TrueForAll(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.TrueForAll(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.Find(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.Find(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.FindLast(dinosaurs, ""{0}""): {1}", _
            Ending, _
            Array.FindLast(dinosaurs, dinoType))

        Console.WriteLine(vbNewLine + _
            "Array.FindAll(dinosaurs, ""{0}""):", Ending)

        Dim subArray() As String = _
            Array.FindAll(dinosaurs, dinoType)

        For Each dinosaur As String In subArray
            Console.WriteLine(dinosaur)
        Next dinosaur
    End Sub

    ' Search predicate returns true if a string ends in "saurus".
    Private Function EndsWithSaurus(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

    ' Search predicate returns true if a string ends in "raptor".
    Private Function EndsWithRaptor(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() = "raptor") Then
            Return True
        Else
            Return False
        End If
    End Function

    ' Search predicate returns true if a string ends in "tops".
    Private Function EndsWithTops(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 > 3) AndAlso _
            (s.Substring(s.Length - 4).ToLower() = "tops") 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, "saurus"): True
'
' Array.TrueForAll(dinosaurs, "saurus"): False
'
' Array.Find(dinosaurs, "saurus"): Amargasaurus
'
' Array.FindLast(dinosaurs, "saurus"): Dilophosaurus
'
' Array.FindAll(dinosaurs, "saurus"):
' Amargasaurus
' Dilophosaurus
C#

using System;

public class DinoDiscoverySet
{
    public static void Main()
    {
        string[] dinosaurs =
        {
            "Compsognathus", "Amargasaurus", "Oviraptor",
            "Velociraptor",  "Deinonychus",  "Dilophosaurus",
            "Gallimimus",    "Triceratops"
        };

        DinoDiscoverySet GoMesozoic = new DinoDiscoverySet(dinosaurs);

        GoMesozoic.DiscoverAll();
        GoMesozoic.DiscoverByEnding("saurus");
    }

    private string[] dinosaurs;

    public DinoDiscoverySet(string[] items)
    {
        dinosaurs = items;
    }

    public void DiscoverAll()
    {
        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }
    }

    public void DiscoverByEnding(string Ending)
    {
        Predicate<string> dinoType;

        switch (Ending.ToLower())
        {
            case "raptor":
                dinoType = EndsWithRaptor;
                break;
            case "tops":
                dinoType = EndsWithTops;
                break;
            case "saurus":
            default:
                dinoType = EndsWithSaurus;
                break;
        }
        Console.WriteLine(
            "\nArray.Exists(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.Exists(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.TrueForAll(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.TrueForAll(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.Find(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.Find(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.FindLast(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array.FindLast(dinosaurs, dinoType));

        Console.WriteLine(
            "\nArray.FindAll(dinosaurs, \"{0}\"):", Ending);

        string[] subArray =
            Array.FindAll(dinosaurs, dinoType);

        foreach(string dinosaur in subArray)
        {
            Console.WriteLine(dinosaur);
        }
    }

    // Search predicate returns true if a string ends in "saurus".
    private bool EndsWithSaurus(string s)
    {
        if ((s.Length > 5) &&
            (s.Substring(s.Length - 6).ToLower() == "saurus"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    // Search predicate returns true if a string ends in "raptor".
    private bool EndsWithRaptor(String s)
    {
        if ((s.Length > 5) &&
            (s.Substring(s.Length - 6).ToLower() == "raptor"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    // Search predicate returns true if a string ends in "tops".
    private bool EndsWithTops(String s)
    {
        if ((s.Length > 3) &&
            (s.Substring(s.Length - 4).ToLower() == "tops"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.Exists(dinosaurs, "saurus"): True

Array.TrueForAll(dinosaurs, "saurus"): False

Array.Find(dinosaurs, "saurus"): Amargasaurus

Array.FindLast(dinosaurs, "saurus"): Dilophosaurus

Array.FindAll(dinosaurs, "saurus"):
Amargasaurus
Dilophosaurus
*/
Visual C++

using namespace System;

public ref class DinoDiscoverySet
{
public:
    static void Main()
    {
        array<String^>^ dinosaurs =
        {
            "Compsognathus", "Amargasaurus", "Oviraptor",
            "Velociraptor",  "Deinonychus",  "Dilophosaurus",
            "Gallimimus",    "Triceratops"
        };

        DinoDiscoverySet^ GoMesozoic = gcnew DinoDiscoverySet(dinosaurs);

        GoMesozoic->DiscoverAll();
        GoMesozoic->DiscoverByEnding("saurus");
    }

    DinoDiscoverySet(array<String^>^ items)
    {
        dinosaurs = items;
    }

    void DiscoverAll()
    {
        Console::WriteLine();
        for each(String^ dinosaur in dinosaurs)
        {
            Console::WriteLine(dinosaur);
        }
    }

    void DiscoverByEnding(String^ Ending)
    {
        Predicate<String^>^ dinoType;

        if (Ending->ToLower() == "raptor")
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithRaptor);
        }
        else if (Ending->ToLower() == "tops")
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithTops);
        }
        else if (Ending->ToLower() == "saurus")
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithSaurus);
        }
        else
        {
            dinoType =
                gcnew Predicate<String^>(&DinoDiscoverySet::EndsWithSaurus);
        }

        Console::WriteLine(
            "\nArray::Exists(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::Exists(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::TrueForAll(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::TrueForAll(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::Find(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::Find(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::FindLast(dinosaurs, \"{0}\"): {1}",
            Ending,
            Array::FindLast(dinosaurs, dinoType));

        Console::WriteLine(
            "\nArray::FindAll(dinosaurs, \"{0}\"):", Ending);

        array<String^>^ subArray =
            Array::FindAll(dinosaurs, dinoType);

        for each(String^ dinosaur in subArray)
        {
            Console::WriteLine(dinosaur);
        }
    }

private:
    array<String^>^ dinosaurs;

    // Search predicate returns true if a string ends in "saurus".
    static bool EndsWithSaurus(String^ s)
    {
        if ((s->Length > 5) &&
            (s->Substring(s->Length - 6)->ToLower() == "saurus"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    // Search predicate returns true if a string ends in "raptor".
    static bool EndsWithRaptor(String^ s)
    {
        if ((s->Length > 5) &&
            (s->Substring(s->Length - 6)->ToLower() == "raptor"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    // Search predicate returns true if a string ends in "tops".
    static bool EndsWithTops(String^ s)
    {
        if ((s->Length > 3) &&
            (s->Substring(s->Length - 4)->ToLower() == "tops"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
};

int main()
{
    DinoDiscoverySet::Main();
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.Exists(dinosaurs, "saurus"): True

Array.TrueForAll(dinosaurs, "saurus"): False

Array.Find(dinosaurs, "saurus"): Amargasaurus

Array.FindLast(dinosaurs, "saurus"): Dilophosaurus

Array.FindAll(dinosaurs, "saurus"):
Amargasaurus
Dilophosaurus
*/
Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

Reference

Array Class
System Namespace
Exists<T>
Predicate<T>