Enumerable.All<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) Method

Definition

判斷序列的所有項目是否全都符合條件。Determines whether all elements of a sequence satisfy a condition.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static bool All(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);
public static bool All<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);
static member All : seq<'Source> * Func<'Source, bool> -> bool
<Extension()>
Public Function All(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As Boolean

Type Parameters

TSource

source 項目的類型。The type of the elements of source.

Parameters

source
IEnumerable<TSource>

IEnumerable<T>,其中包含要套用述詞 (Predicate) 的項目。An IEnumerable<T> that contains the elements to apply the predicate to.

predicate
Func<TSource,Boolean>

用來測試每個項目是否符合條件的函式。A function to test each element for a condition.

Returns

Boolean

如果來源序列的每個項目都通過以指定之述詞 (Predicate) 進行的測試,或序列是空的,則為 true,否則為 falsetrue if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.

Exceptions

sourcepredicatenullsource or predicate is null.

Examples

下列程式碼範例示範如何使用 All 來判斷序列中的所有元素是否都符合條件。The following code example demonstrates how to use All to determine whether all the elements in a sequence satisfy a condition. 如果所有寵物名稱的開頭都是 "B",或 pets 陣列是空的,則變數 allStartWithB 為 true。Variable allStartWithB is true if all the pet names start with "B" or if the pets array is empty.

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void AllEx()
{
    // Create an array of Pets.
    Pet[] pets = { new Pet { Name="Barley", Age=10 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=6 } };

    // Determine whether all pet names
    // in the array start with 'B'.
    bool allStartWithB = pets.All(pet =>
                                      pet.Name.StartsWith("B"));

    Console.WriteLine(
        "{0} pet names start with 'B'.",
        allStartWithB ? "All" : "Not all");
}

// This code produces the following output:
//
//  Not all pet names start with 'B'.
Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Sub AllEx()
    ' Create an array of Pets.
    Dim pets() As Pet =
{New Pet With {.Name = "Barley", .Age = 2},
 New Pet With {.Name = "Boots", .Age = 4},
 New Pet With {.Name = "Whiskers", .Age = 7}}

    ' Determine whether all pet names in the array start with "B".
    Dim allNames As Boolean =
pets.All(Function(ByVal pet) pet.Name.StartsWith("B"))

    ' Display the output.
    Dim text As String = IIf(allNames, "All", "Not all")
    Console.WriteLine($"{text} pet names start with 'B'.")
End Sub

' This code produces the following output:
'
' Not all pet names start with 'B'.

All 方法傳回的布林值通常用於 where 子句的述詞(Visual Basic 中的Where 子句),或直接呼叫 Where 方法。The Boolean value that the All method returns is typically used in the predicate of a where clause (Where clause in Visual Basic) or a direct call to the Where method. 下列範例示範如何使用 All 方法。The following example demonstrates this use of the All method.

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}
class Person
{
    public string LastName { get; set; }
    public Pet[] Pets { get; set; }
}

public static void AllEx2()
{
    List<Person> people = new List<Person>
        { new Person { LastName = "Haas",
                       Pets = new Pet[] { new Pet { Name="Barley", Age=10 },
                                          new Pet { Name="Boots", Age=14 },
                                          new Pet { Name="Whiskers", Age=6 }}},
          new Person { LastName = "Fakhouri",
                       Pets = new Pet[] { new Pet { Name = "Snowball", Age = 1}}},
          new Person { LastName = "Antebi",
                       Pets = new Pet[] { new Pet { Name = "Belle", Age = 8} }},
          new Person { LastName = "Philips",
                       Pets = new Pet[] { new Pet { Name = "Sweetie", Age = 2},
                                          new Pet { Name = "Rover", Age = 13}} }
        };

    // Determine which people have pets that are all older than 5.
    IEnumerable<string> names = from person in people
                                where person.Pets.All(pet => pet.Age > 5)
                                select person.LastName;

    foreach (string name in names)
    {
        Console.WriteLine(name);
    }

    /* This code produces the following output:
     *
     * Haas
     * Antebi
     */
}
Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Structure Person
    Public LastName As String
    Public Pets() As Pet
End Structure

Sub AllEx2()
    Dim people As New List(Of Person)(New Person() _
{New Person With {.LastName = "Haas",
                  .Pets = New Pet() {New Pet With {.Name = "Barley", .Age = 10},
                                     New Pet With {.Name = "Boots", .Age = 14},
                                     New Pet With {.Name = "Whiskers", .Age = 6}}},
  New Person With {.LastName = "Fakhouri",
                   .Pets = New Pet() {New Pet With {.Name = "Snowball", .Age = 1}}},
  New Person With {.LastName = "Antebi",
                   .Pets = New Pet() {New Pet With {.Name = "Belle", .Age = 8}}},
  New Person With {.LastName = "Philips",
                   .Pets = New Pet() {New Pet With {.Name = "Sweetie", .Age = 2},
                                      New Pet With {.Name = "Rover", .Age = 13}}}})

    ' Determine which people have pets that are all older than 5.
    Dim names = From person In people
                Where person.Pets.All(Function(pet) pet.Age > 5)
                Select person.LastName

    For Each name As String In names
        Console.WriteLine(name)
    Next

    ' This code produces the following output:
    '
    ' Haas
    ' Antebi

End Sub

Remarks

Note

這個方法不會傳回集合的所有元素。This method does not return all the elements of a collection. 相反地,它會判斷集合的所有元素是否都符合條件。Instead, it determines whether all the elements of a collection satisfy a condition.

一旦可以判斷結果,source 的列舉就會停止。The enumeration of source is stopped as soon as the result can be determined.

在 Visual Basic 查詢運算式語法中,Aggregate Into All() 子句會轉譯為 All的調用。In Visual Basic query expression syntax, an Aggregate Into All() clause translates to an invocation of All.

Applies to

See also