Enumerable.LongCount 方法
定义
重要
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返回表示序列中的元素数量的 Int64。
重载
LongCount<TSource>(IEnumerable<TSource>) |
返回表示序列中元素总数的 Int64。 |
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。 |
LongCount<TSource>(IEnumerable<TSource>)
- Source:
- Count.cs
- Source:
- Count.cs
- Source:
- Count.cs
返回表示序列中元素总数的 Int64。
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。
参数
- source
- IEnumerable<TSource>
包含要进行计数的元素的 IEnumerable<T>。
返回
源序列中的元素数量。
例外
source
为 null
。
元素数超过 Int64.MaxValue。
示例
下面的代码示例演示如何使用 LongCount<TSource>(IEnumerable<TSource>) 对数组中的元素进行计数。
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
使用此方法,而不是 Count 在预期结果大于 MaxValue时使用 。
在 Visual Basic 查询表达式语法中, Aggregate Into LongCount()
子句转换为 的调用 LongCount。
另请参阅
适用于
LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
- Source:
- Count.cs
- Source:
- Count.cs
- Source:
- Count.cs
返回表示序列中满足条件的元素的数量的 Int64。
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。
参数
- source
- IEnumerable<TSource>
包含要进行计数的元素的 IEnumerable<T>。
返回
一个数字,表示序列中满足谓词函数条件的元素数量。
例外
source
或 predicate
为 null
。
匹配的元素数超过 Int64.MaxValue。
示例
下面的代码示例演示如何使用 LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) 对满足条件的数组中的元素进行计数。
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
使用此方法,而不是 Count 在预期结果大于 MaxValue时使用 。
在 Visual Basic 查询表达式语法中, Aggregate Into LongCount()
子句转换为 的调用 LongCount。