为什么C＃split给我一个以空行结尾的数组？

Question

I have the following expression:

"<p>What ?</p>\n<pre>Starting Mini</pre>"

When I perform a split as follows:

   var split = content
      .Split(new[] { "<pre>", "</pre>" }, StringSplitOptions.None);

Then it gives me three entries:

"<p>What ?</p>\n"
"Starting Mini"
""

Why does it give an empty line as the third entry and how can I avoid this?

Answer 1

The "why" is simply: the input (if you don't remove empty entries) will always "split" at any occurrence of the separator(s), so if the separator(s) appear n times in the string, then the array will be n+1 long. In particular, this essentially lets you know where they occurred in the original string (although when using multiple separators, it doesn't let you know which appeared where).

For example, with a simple example (csv without any escaping etc):

string[] arr = input.Split(','); // even if something like "a,b,c,d,"
// which allows...
int numberOfCommas = arr.Length - 1;
string original = string.Join(",", arr);

The fix is, as already mentioned, to use RemoveEmptyEntries .

Answer 2

Use StringSplitOptions.RemoveEmptyEntries instead to remove empty string in list

 var split = content
  .Split(new[] { "<pre>", "</pre>" }, StringSplitOptions.RemoveEmptyEntries);

Answer 3

You get this behaviour as specified from Microsoft: "Adjacent delimiters yield an array element that contains an empty string ("")." So since you have the last pre you get the last empty array element

Answer 4

The reason you are getting this behaviour is that your one of the delimeter </pre> happens to exist at the end of the string .

You may see: string.Split - MSDN

... a delimiter is found at the beginning or end of this instance, the corresponding array element contains Empty

To overcome this:

Use StringSplitOptions.RemoveEmptyEntries instead of StringSplitOptions.None

StringSplitOptions.RemoveEmptyEntries - MSDN

The return value does not include array elements that contain an empty string

 var split = content
       .Split(new[] { "<pre>", "</pre>" }, StringSplitOptions.RemoveEmptyEntries);

Answer 5

Mailou, instead of giving 'StringSplitOptions.None' try 'StringSplitOptions.RemoveEmptyEntries'. It removes the the empty lines.

Answer 6

您还需要指定

StringSplitOptions.RemoveEmptyEntries enumerator.

Answer 7

The split string[] values not include any empty string by using StringSplitOptions.RemoveEmptyEntries

var split = content
  .Split(new[] { "<pre>", "</pre>" }, StringSplitOptions.RemoveEmptyEntries);

Reference: StringSplitOptions Enumeration

Answer 8

You are getting empty line due to

</pre>

You are instructing split function to split by <pre> and </pre>

As result with <pre> you are getting

<p>What ?</p>\n
Starting Mini</pre>

And next result is with </pre> is

<p>What ?</p>\n
Starting Mini
...