C＃LINQ：如何字符串（QUOT; [1，2，3] QUOT;）解析为一个数组？ [英] C# LINQ: How is string("[1, 2, 3]") parsed as an array?

问题描述

我试图解析字符串到数组，并找到一个非常简洁的方法。

I am trying to parse a string into array and find a very concise approach.

string line = "[1, 2, 3]";
string[] input = line.Substring(1, line.Length - 2).Split();
int[] num = input.Skip(2)
                 .Select(y => int.Parse(y))
                 .ToArray();

我试图删除跳过（2），我不能得到，因为非INT字符串数组。我的问题是，什么是这些LINQ函数的执行顺序。多少次被跳过这里叫什么名字？

I tried remove Skip(2) and I cannot get the array because of non-int string. My question is that what is the execution order of those LINQ function. How many times is Skip called here?

先谢谢了。

推荐答案

该订单是您指定的顺序。因此， input.Skip（2）跳过数组中的前两个字符串，因此只有最后遗迹，是 3 。可以分析到 INT 。如果删除跳到（2）您正试图解析他们。这并不工作，因为逗号仍然存在。您已通过的空格分裂，但不会删除逗号。

The order is the order that you specify. So input.Skip(2) skips the first two strings in the array, so only the last remains which is 3. That can be parsed to an int. If you remove the Skip(2) you are trying to parse all of them. That doesn't work because the commas are still there. You have splitted by white-spaces but not removed the commas.

您可以使用 line.Trim（'['，']'）。斯普利特（''）; 和 int.TryParse ：

string line = "[1, 2, 3]";
string[] input = line.Trim('[', ']').Split(',');
int i = 0;
int[] num = input.Where(s => int.TryParse(s, out i)) // you could use s.Trim but the spaces don't hurt
                 .Select(s => i)
                 .ToArray(); 

只是为了澄清，我已经使用 int.TryParse 只，以确保如果输入包含无效数据，你没有得到一个例外。它没有任何修复。它还将与 int.Parse 工作

Just to clarify, i have used int.TryParse only to make sure that you don't get an exception if the input contains invalid data. It doesn't fix anything. It would also work with int.Parse.

更新：作为已被证明通过埃里克利珀的在注释部分在LINQ查询中使用 int.TryParse 可能是有害的。因此，最好使用一个封装 int.TryParse 并返回可空℃的helper方法; INT> 。因此，一个扩展是这样的：

Update: as has been proved by Eric Lippert in the comment section using int.TryParse in a LINQ query can be harmful. So it's better to use a helper method that encapsulates int.TryParse and returns a Nullable<int>. So an extension like this:

public static int? TryGetInt32(this string item)
{
    int i;
    bool success = int.TryParse(item, out i);
    return success ? (int?)i : (int?)null;
}

现在，你可以在这样一个LINQ查询使用它：

Now you can use it in a LINQ query in this way:

string line = "[1, 2, 3]";
string[] input = line.Trim('[', ']').Split(',');
int[] num = input.Select(s => s.TryGetInt32())
                 .Where(n => n.HasValue)
                 .Select(n=> n.Value)
                 .ToArray();

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