Enumerable.All<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)
Determines whether all elements of a sequence satisfy a condition.
Assembly: System.Core (in System.Core.dll)
public static bool All<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate )
Parameters
- source
-
Type:
System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> that contains the elements to apply the predicate to.
- predicate
-
Type:
System.Func<TSource, Boolean>
A function to test each element for a condition.
Return Value
Type: System.Booleantrue if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.
Type Parameters
- TSource
The type of the elements of source.
| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is null. |
Note |
|---|
This method does not return all the elements of a collection. Instead, it determines whether all the elements of a collection satisfy a condition. |
The enumeration of source is stopped as soon as the result can be determined.
In Visual Basic query expression syntax, an Aggregate Into All() clause translates to an invocation of All<TSource>.
The following code example demonstrates how to use All<TSource> to determine whether all the elements in a sequence satisfy a condition. 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'.
The Boolean value that the All<TSource> method returns is typically used in the predicate of a where clause (Where clause in Visual Basic) or a direct call to the Where<TSource> method. 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 */ }
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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