Enumerable.LongCount 方法
定义
重载
| LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) |
返回表示序列中满足条件的元素的数量的 Int64。Returns an Int64 that represents how many elements in a sequence satisfy a condition. |
| LongCount<TSource>(IEnumerable<TSource>) |
返回表示序列中元素总数的 Int64。Returns an Int64 that represents the total number of elements in a sequence. |
LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static long LongCount(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);public static long LongCount<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);static member LongCount : seq<'Source> * Func<'Source, bool> -> int64<Extension()>
Public Function LongCount(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As Long类型参数
- TSource
source 的元素类型。The type of the elements of source.
参数
- source
- IEnumerable<TSource>
包含要进行计数的元素的 IEnumerable<T>。An IEnumerable<T> that contains the elements to be counted.
返回
一个数字，表示序列中满足谓词函数条件的元素数量。A number that represents how many elements in the sequence satisfy the condition in the predicate function.
例外
source 或 predicate 为 null。source or predicate is null.
示例
下面的代码示例演示如何使用 LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) 来计算数组中满足条件的元素。The following code example demonstrates how to use LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to count the elements in an array that satisfy a condition.
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
}
public static void LongCountEx2()
{
Pet[] pets = { new Pet { Name="Barley", Age=8 },
new Pet { Name="Boots", Age=4 },
new Pet { Name="Whiskers", Age=1 } };
const int Age = 3;
long count = pets.LongCount(pet => pet.Age > Age);
Console.WriteLine("There are {0} animals over age {1}.", count, Age);
}
/*
This code produces the following output:
There are 2 animals over age 3.
*/
Structure Pet
Public Name As String
Public Age As Integer
End Structure
Sub LongCountEx2()
' Create a list of Pet objects.
Dim pets As New List(Of Pet)(New Pet() _
{New Pet With {.Name = "Barley", .Age = 8},
New Pet With {.Name = "Boots", .Age = 4},
New Pet With {.Name = "Whiskers", .Age = 1}})
' Determine the number of elements in the list
' where the pet's age is greater than a constant value (3).
Const Age As Integer = 3
Dim count As Long =
pets.LongCount(Function(pet) pet.Age > Age)
' Display the result.
Console.WriteLine($"There are {count} animals over age {Age}")
End Sub
' This code produces the following output:
'
' There are 2 animals over age 3
注解
如果希望结果大于，请使用此方法而不是 Count MaxValue 。Use this method rather than Count when you expect the result to be greater than MaxValue.
在 Visual Basic 查询表达式语法中， Aggregate Into LongCount() 子句转换为对的调用 LongCount 。In Visual Basic query expression syntax, an Aggregate Into LongCount() clause translates to an invocation of LongCount.
另请参阅
适用于
LongCount<TSource>(IEnumerable<TSource>)
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static long LongCount(System::Collections::Generic::IEnumerable<TSource> ^ source);public static long LongCount<TSource> (this System.Collections.Generic.IEnumerable<TSource> source);static member LongCount : seq<'Source> -> int64<Extension()>
Public Function LongCount(Of TSource) (source As IEnumerable(Of TSource)) As Long类型参数
- TSource
source 的元素类型。The type of the elements of source.
参数
- source
- IEnumerable<TSource>
包含要进行计数的元素的 IEnumerable<T>。An IEnumerable<T> that contains the elements to be counted.
返回
源序列中的元素数量。The number of elements in the source sequence.
例外
source 为 null。source is null.
示例
下面的代码示例演示如何使用 LongCount<TSource>(IEnumerable<TSource>) 来计算数组中元素的数目。The following code example demonstrates how to use LongCount<TSource>(IEnumerable<TSource>) to count the elements in an array.
string[] fruits = { "apple", "banana", "mango",
"orange", "passionfruit", "grape" };
long count = fruits.LongCount();
Console.WriteLine("There are {0} fruits in the collection.", count);
/*
This code produces the following output:
There are 6 fruits in the collection.
*/
' Create an array of strings.
Dim fruits() As String =
{"apple", "banana", "mango", "orange", "passionfruit", "grape"}
' Get the number of items in the array.
Dim count As Long = fruits.LongCount()
' Display the result.
Console.WriteLine($"There are {count} fruits in the collection.")
' This code produces the following output:
'
' There are 6 fruits in the collection.
注解
如果希望结果大于，请使用此方法而不是 Count MaxValue 。Use this method rather than Count when you expect the result to be greater than MaxValue.
在 Visual Basic 查询表达式语法中， Aggregate Into LongCount() 子句转换为对的调用 LongCount 。In Visual Basic query expression syntax, an Aggregate Into LongCount() clause translates to an invocation of LongCount.