收益率 [英] yield return

问题描述

我正在使用yield return的可枚举函数。这允许我遍历每个循环使用的项目。由于这是一个惰性求值，每次迭代后控件都会返回到调用函数。

如何在没有每个循环的情况下使用可枚举函数？

public static IEnumerable< int> GetValuesUpto（int n）
{

for（int ctr = 1; ctr< = n; ctr ++）
{
yield return ctr;
}
}

所以，当我调用这个函数时，
int [] arr = GetValuesUpto（10）;

结果是什么，它会像懒惰的评估一样工作，只返回第一个值，还是会返回所需的结果？

等待你的回复人!!
Vishwjeet

Hi,
I am using a enumerable function using "yield return". This allows me to iterate through the items using for each loop. Since this is a lazy evaluation, after each iteration the control returns to the calling function.

How can I use the enumerable function without for each loop?

public static IEnumerable<int> GetValuesUpto(int n)
{

for(int ctr = 1;ctr<=n;ctr++)
{
yield return ctr;
}
}

So, when I call this function i.e.
int[] arr = GetValuesUpto(10);

What would be the result, will it work like a lazy evaluation and will return only the first value, or will it return the desired result?

Waiting for your replies guys!!
Vishwjeet

推荐答案

当你调用迭代器块时想要从Enumerable中获取数据。

实际上如果你调用该函数，它将不会被调用。相反，如果你对Enumerable对象进行foreach，那么函数将被调用并将返回10. ;-)

只需像我一样改变你的代码：

Iterator blocks are called when you want to fetch the data from the Enumerable.

Actually if you call the the function, it will not be called. Rather if you do a foreach on the Enumerable object the function will be called and will return you 10. ;-)

Just change your code a bit as I did:

<br />IEnumerable<int> arr = Documented.GetValuesUpto(10);<br />MessageBox.Show(arr.ToList<int>().Count.ToString());

public static IEnumerable<int> GetValuesUpto(int n)<br />{<br /><br />    for (int ctr = 1; ctr <= n; ctr++)<br />    {<br /><br />       yield return ctr;<br />    }<br />            <br />}

在行中放置一个断点 IEnumerable< int> arr = Documented.GetValuesUpto（10）; 。以及 GetValueUpto 块内的断点。当我们尝试调用 ToList （）而不是实际调用 GetValueUpto 时，您将看到调用该函数。这是迭代器块的主要优点。

[玫瑰] [玫瑰]

Put a breakpoint in the line IEnumerable<int> arr = Documented.GetValuesUpto(10);. and also a breakpoint within GetValueUpto block. You will see the function is called when we try to call ToList() rather than the actual call to GetValueUpto. This is the main advantage of iterator blocks.

[Rose][Rose]

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