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

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

參數

傳回

IEnumerable<TSource>

IEnumerable<T>，其中包含輸入序列開頭處指定的項目數目。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 ，從序列的開頭傳回元素。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
Console.WriteLine(output.ToString())

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

備註

這個方法是使用延後執行所執行。This method is implemented by using deferred execution. 立即傳回值是一個物件，它會儲存執行動作所需的所有資訊。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，直到以 GetEnumerator foreach Visual c # 或 Visual Basic 中的方法來列舉物件為止 For Each 。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 和產生元素，直到產生 count 元素或 source 不包含其他元素為止。Take enumerates source and yields elements until count elements have been yielded or source contains no more elements. 如果 count 超過中的專案數 source ， source 則會傳回的所有元素。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 則不會列舉，而且會傳回空白 IEnumerable<T> 。If count is less than or equal to zero, source is not enumerated and an empty IEnumerable<T> is returned.

Take和 Skip 方法的功能可補充。The Take and Skip methods are functional complements. 指定序列 coll 和整數 n ，串連的結果 coll.Take(n) 和 coll.Skip(n) 產生與相同的順序 coll 。Given 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 子句會轉譯為的調用 Take 。In Visual Basic query expression syntax, a Take clause translates to an invocation of Take.

適用於

另請參閱

• Take 子句 (Visual Basic)Take Clause (Visual Basic)