Enumerable.SkipWhile 方法

定义

如果指定的条件为 true,则跳过序列中的元素,然后返回剩余的元素。Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.

重载

SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

如果指定的条件为 true,则跳过序列中的元素,然后返回剩余的元素。Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.

SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)

如果指定的条件为 true,则跳过序列中的元素,然后返回剩余的元素。Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. 将在谓词函数的逻辑中使用元素的索引。The element's index is used in the logic of the predicate function.

SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

如果指定的条件为 true,则跳过序列中的元素,然后返回剩余的元素。Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ SkipWhile(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);
public static System.Collections.Generic.IEnumerable<TSource> SkipWhile<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);
static member SkipWhile : seq<'Source> * Func<'Source, bool> -> seq<'Source>
<Extension()>
Public Function SkipWhile(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As IEnumerable(Of TSource)

类型参数

TSource

source 的元素类型。The type of the elements of source.

参数

source
IEnumerable<TSource>

要从中返回元素的 IEnumerable<T>An IEnumerable<T> to return elements from.

predicate
Func<TSource,Boolean>

用于测试每个元素是否满足条件的函数。A function to test each element for a condition.

返回

IEnumerable<TSource>

一个 IEnumerable<T>,包含输入序列中的元素,该输入序列从线性系列中没有通过 predicate 指定测试的第一个元素开始。An IEnumerable<T> that contains the elements from the input sequence starting at the first element in the linear series that does not pass the test specified by predicate.

异常

sourcepredicatenullsource or predicate is null.

示例

下面的代码示例演示了在条件为 true 的情况下,如何使用 SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) 跳过数组的元素。The following code example demonstrates how to use SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to skip elements of an array as long as a condition is true.

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

IEnumerable<int> lowerGrades =
    grades
    .OrderByDescending(grade => grade)
    .SkipWhile(grade => grade >= 80);

Console.WriteLine("All grades below 80:");
foreach (int grade in lowerGrades)
{
    Console.WriteLine(grade);
}

/*
 This code produces the following output:

 All grades below 80:
 70
 59
 56
*/
' Create an array of integers that represent grades.
Dim grades() As Integer = {59, 82, 70, 56, 92, 98, 85}

' Sort the grades in descending order and
' get all grades greater less than 80.
Dim lowerGrades As IEnumerable(Of Integer) =
grades _
.OrderByDescending(Function(grade) grade) _
.SkipWhile(Function(grade) grade >= 80)

' Display the results.
Dim output As New System.Text.StringBuilder("All grades below 80:" & vbCrLf)
For Each grade As Integer In lowerGrades
    output.AppendLine(grade)
Next
Console.WriteLine(output.ToString())

' This code produces the following output:
'
' All grades below 80:
' 70
' 59
' 56

注解

SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) 方法是使用延迟执行实现的。The SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) method is implemented by using deferred execution. 即时返回值是一个对象,该对象存储执行操作所需的所有信息。The immediate return value is an object that stores all the information that is required to perform the action. 此方法表示的查询在枚举对象之前不会执行,方法是通过直接调用 GetEnumerator 方法或在 Visual Basic 中使用视觉C#对象中的 foreachFor Each 来枚举对象。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.

此方法使用 predicate 测试 source 的每个元素,如果结果 true,则跳过元素。This method tests each element of source by using predicate and skips the element if the result is true. 在谓词函数为元素返回 false 后,将生成该元素和 source 中剩余的元素,并且不会对 predicate进行更多的调用。After the predicate function returns false for an element, that element and the remaining elements in source are yielded and there are no more invocations of predicate.

如果 predicate 为序列中的所有元素返回 true,则返回空的 IEnumerable<T>If predicate returns true for all elements in the sequence, an empty IEnumerable<T> is returned.

TakeWhileSkipWhile 方法是功能补充。The TakeWhile and SkipWhile methods are functional complements. 给定一个序列 coll 和一个纯函数 p,将 coll.TakeWhile(p)coll.SkipWhile(p) 的结果连接起来与 coll生成相同的序列。Given a sequence coll and a pure function p, concatenating the results of coll.TakeWhile(p) and coll.SkipWhile(p) yields the same sequence as coll.

在 Visual Basic 查询表达式语法中,Skip While 子句会转换为 SkipWhile调用。In Visual Basic query expression syntax, a Skip While clause translates to an invocation of SkipWhile.

另请参阅

SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)

如果指定的条件为 true,则跳过序列中的元素,然后返回剩余的元素。Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. 将在谓词函数的逻辑中使用元素的索引。The element's index is used in the logic of the predicate function.

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

类型参数

TSource

source 的元素类型。The type of the elements of source.

参数

source
IEnumerable<TSource>

要从中返回元素的 IEnumerable<T>An IEnumerable<T> to return elements from.

predicate
Func<TSource,Int32,Boolean>

用于测试每个源元素是否满足条件的函数;该函数的第二个参数表示源元素的索引。A function to test each source element for a condition; the second parameter of the function represents the index of the source element.

返回

IEnumerable<TSource>

一个 IEnumerable<T>,包含输入序列中的元素,该输入序列从线性系列中没有通过 predicate 指定测试的第一个元素开始。An IEnumerable<T> that contains the elements from the input sequence starting at the first element in the linear series that does not pass the test specified by predicate.

异常

sourcepredicatenullsource or predicate is null.

示例

下面的代码示例演示如何使用 SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) 跳过数组中的元素,前提是该元素的索引为 true 的条件。The following code example demonstrates how to use SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) to skip elements of an array as long as a condition that depends on the element's index is true.

int[] amounts = { 5000, 2500, 9000, 8000, 
                    6500, 4000, 1500, 5500 };

IEnumerable<int> query =
    amounts.SkipWhile((amount, index) => amount > index * 1000);

foreach (int amount in query)
{
    Console.WriteLine(amount);
}

/*
 This code produces the following output:

 4000
 1500
 5500
*/
' Create an array of integers.
Dim amounts() As Integer =
{5000, 2500, 9000, 8000, 6500, 4000, 1500, 5500}

' Skip items in the array whose value is greater than
' the item's index times 1000; get the remaining items.
Dim query As IEnumerable(Of Integer) =
amounts.SkipWhile(Function(amount, index) _
                      amount > index * 1000)

' Output the results.
Dim output As New System.Text.StringBuilder
For Each amount As Integer In query
    output.AppendLine(amount)
Next
Console.WriteLine(output.ToString())

' This code produces the following output:
'
' 4000
' 1500
' 5500

注解

此方法是使用延迟执行实现的。This method is implemented by using deferred execution. 即时返回值是一个对象,该对象存储执行操作所需的所有信息。The immediate return value is an object that stores all the information that is required to perform the action. 此方法表示的查询在枚举对象之前不会执行,方法是通过直接调用 GetEnumerator 方法或在 Visual Basic 中使用视觉C#对象中的 foreachFor Each 来枚举对象。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.

SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) 方法使用 predicate 测试 source 的每个元素,并在结果为 true时跳过元素。The SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) method tests each element of source by using predicate and skips the element if the result is true. 在谓词函数为元素返回 false 后,将生成该元素和 source 中剩余的元素,并且不会对 predicate进行更多的调用。After the predicate function returns false for an element, that element and the remaining elements in source are yielded and there are no more invocations of predicate.

如果 predicate 为序列中的所有元素返回 true,则返回空的 IEnumerable<T>If predicate returns true for all elements in the sequence, an empty IEnumerable<T> is returned.

predicate 的第一个参数表示要测试的元素。The first argument of predicate represents the element to test. 第二个参数表示 source内元素的从零开始的索引。The second argument represents the zero-based index of the element within source.

TakeWhileSkipWhile 方法是功能补充。The TakeWhile and SkipWhile methods are functional complements. 给定一个序列 coll 和一个纯函数 p,将 coll.TakeWhile(p)coll.SkipWhile(p) 的结果连接起来与 coll生成相同的序列。Given a sequence coll and a pure function p, concatenating the results of coll.TakeWhile(p) and coll.SkipWhile(p) yields the same sequence as coll.

在 Visual Basic 查询表达式语法中,Skip While 子句会转换为 SkipWhile调用。In Visual Basic query expression syntax, a Skip While clause translates to an invocation of SkipWhile.

另请参阅

适用于