Regex not working in .NET

Question

So I'm trying to match up a regex and I'm fairly new at this. I used a validator and it works when I paste the code but not when it's placed in the codebehind of a .NET2.0 C# page.

The offending code is supposed to be able to split on a single semi-colon but not on a double semi-colon. However, when I used the string

"entry;entry2;entry3;entry4;"

I get a nonsense array that contains empty values, the last letter of the previous entry, and the semi-colons themselves. The online javascript validator splits it correctly. Please help!

My regex:

((;;|[^;])+)

Answer 1

Split on the following regular expression:

(?<!;);(?!;)

It means match semicolons that are neither preceded nor succeeded by another semicolon.

For example, this code

var input = "entry;entry2;entry3;entry4;";
foreach (var s in Regex.Split(input, @"(?<!;);(?!;)"))
    Console.WriteLine("[{0}]", s);

produces the following output:

[entry]
[entry2]
[entry3]
[entry4]
[]

The final empty field is a result of the semicolon on the end of the input.

If the semicolon is a terminator at the end of each field rather than a separator between consecutive fields, then use Regex.Matches instead

foreach (Match m in Regex.Matches(input, @"(.+?)(?<!;);(?!;)"))
    Console.WriteLine("[{0}]", m.Groups[1].Value);

to get

[entry]
[entry2]
[entry3]
[entry4]

Answer 2

Why not use String.Split on the semicolon?

string sInput = "Entry1;entry2;entry3;entry4";
string[] sEntries = sInput.Split(';');
// Do what you have to do with the entries in the array...

Hope this helps, Best regards, Tom.

Answer 3

As tommieb75 wrote, you can use String.Split with StringSplitOptions Enumeration so you can control your output of newly created splitting array

string input = "entry1;;entry2;;;entry3;entry4;;";
char[] charSeparators = new char[] {';'};
// Split a string delimited by characters and return all non-empty elements.
result = input.Split(charSeparators, StringSplitOptions.RemoveEmptyEntries);

The result would contain only 4 elements like this:

<entry1><entry2><entry3><entry4>