Enumerable.Take(IEnumerable<TSource>, Int32) Enumerable.Take(IEnumerable<TSource>, Int32) Enumerable.Take(IEnumerable<TSource>, Int32) Enumerable.Take(IEnumerable<TSource>, Int32) Method

定義

從序列開頭傳回指定的數目的連續項目。Returns a specified number of contiguous elements from the start of a sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ Take(System::Collections::Generic::IEnumerable<TSource> ^ source, int count);
public static System.Collections.Generic.IEnumerable<TSource> Take<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, int count);
static member Take : seq<'Source> * int -> seq<'Source>
<Extension()>
Public Function Take(Of TSource) (source As IEnumerable(Of TSource), count As Integer) As IEnumerable(Of TSource)

類型參數

TSource

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

參數

source
IEnumerable<TSource>

傳回項目的序列。The sequence to return elements from.

count
Int32 Int32 Int32 Int32

要傳回的項目數目。The number of elements to return.

傳回

IEnumerable<TSource>

IEnumerable<T> ,包含從輸入序列的開頭指定項目數。An IEnumerable<T> that contains the specified number of elements from the start of the input sequence.

例外狀況

範例

下列程式碼範例示範如何使用Take從序列開頭傳回項目。The following code example demonstrates how to use Take to return elements from the start of a sequence.

int[] grades = { 59, 82, 70, 56, 92, 98, 85 };

IEnumerable<int> topThreeGrades =
    grades.OrderByDescending(grade => grade).Take(3);

Console.WriteLine("The top three grades are:");
foreach (int grade in topThreeGrades)
{
    Console.WriteLine(grade);
}
/*
 This code produces the following output:

 The top three grades are:
 98
 92
 85
*/
' Create an array of Integer values that represent grades.
Dim grades() As Integer = {59, 82, 70, 56, 92, 98, 85}

' Get the highest three grades by first sorting
' them in descending order and then taking the
' first three values.
Dim topThreeGrades As IEnumerable(Of Integer) =
grades _
.OrderByDescending(Function(grade) grade) _
.Take(3)

' Display the results.
Dim output As New System.Text.StringBuilder("The top three grades are:" & vbCrLf)
For Each grade As Integer In topThreeGrades
    output.AppendLine(grade)
Next
MsgBox(output.ToString())

' This code produces the following output:
'
' The top three grades are:
' 98
' 92
' 85

備註

實作這個方法是使用延後的執行。This method is implemented by using deferred execution. 立即傳回值是儲存,才能執行此動作的所有資訊的物件。The immediate return value is an object that stores all the information that is required to perform the action. 這個方法所表示的查詢不會執行直到列舉物件可以藉由呼叫其GetEnumerator方法直接或透過foreachVisual C# 中或For EachVisual Basic 中。The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

Take 列舉source產生項目,直到count項目已產生或source未包含多個項目。Take enumerates source and yields elements until count elements have been yielded or source contains no more elements. 如果count超過中的項目數source的所有項目source會傳回。If count exceeds the number of elements in source, all elements of source are returned.

如果count小於或等於零,source不是列舉和空白IEnumerable<T>會傳回。If count is less than or equal to zero, source is not enumerated and an empty IEnumerable<T> is returned.

TakeSkip方法都是功能補充項目。The Take and Skip methods are functional complements. 從指定的序列coll和一個整數n,串連的結果coll.Take(n)coll.Skip(n)會產生相同的順序為collGiven a sequence coll and an integer n, concatenating the results of coll.Take(n) and coll.Skip(n) yields the same sequence as coll.

在 Visual Basic 查詢運算式語法中,Take子句會轉譯成的引動過程TakeIn Visual Basic query expression syntax, a Take clause translates to an invocation of Take.

適用於

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