Converting regular expression from java to .Net

Question

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Hi,

I'm converting a project from java to C#. I have no idea what the equivalence of following regular expression would be in C#.

The regular expression : Customer rating (?<rating>\d.\d)/5.0
The java string : "Customer rating (?<rating>\\d.\\d)/5.0"

This is the java code:

Java

private static final Pattern ratingPattern = Pattern.compile("Customer rating (?<rating>\\d.\\d)/5.0");
...
m = Retriever.ratingPattern.matcher(X);
if (m.matches()) {
...
}

and it works for ( X=Customer rating 1.0/5.0 ). But this is the C# code:

C#

static Regex rx = new Regex(@"Customer rating (?<rating>\\d.\\d)/5.0");
...
MatchCollection matches = rx.Matches(X);
if (matches.Count > 0)
{
...
}

and it doesn't work for ( X=Customer rating 1.0/5.0 ).I mean (Matches.count) is always 0 for ( X=Customer rating 1.0/5.0 )

Please help me if you have any ideas.

Thank you
Saman

Posted 7-Nov-14 3:20am

Saman With You

Updated 7-Nov-14 4:57am

PIEBALDconsult

v5

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Comments

PIEBALDconsult 7-Nov-14 9:34am

You may want to escape the dots.

PIEBALDconsult 7-Nov-14 10:45am

I get
System.ArgumentException: parsing "Customer rating (?\\d.\\d)/5.0" - Unrecognized grouping construct.

Edit: That was because the code you posted left off the name of the group (rating) -- I fixed it.

First, remove the @, you don't need it when you have the backslashes escaped already.

Saman With You 7-Nov-14 10:48am

Great! I removed @ and it was solved! Now it works! Thank you so much.

PIEBALDconsult 7-Nov-14 10:51am

OK, but you should still escape the dots in the pattern; they mean "any character" and you probably want to match actual dots.

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Manas Bhardwaj · Answer 1 · 2014-11-07T03:23:00

Solution 1

Regular Expressions[^] do not change for a different language.

The current regular expression in it's form should work in C# as well.

Posted 7-Nov-14 3:23am

Manas Bhardwaj

Comments

PIEBALDconsult 7-Nov-14 9:33am

My understanding is that Regular Expressions in .net has a few more features than some other implementations.
I don't know about Java.

Saman With You 7-Nov-14 9:38am

Yes. It doesn't find any matches in C# when I copy the same string as "Matches" method parameter.

PIEBALDconsult 7-Nov-14 9:39am

Provide some examples. Have you tried Expresso?

Saman With You 7-Nov-14 9:51am

No, How can I use it for this problem?

Saman With You 7-Nov-14 9:47am

This is the java code:

private static final Pattern ratingPattern = Pattern.compile("Customer rating (?<rating>\\d.\\d)/5.0");
...
m = Retriever.ratingPattern.matcher(X);
if (m.matches()) {
...
}

and it works. But this is the C# code:

static Regex rx = new Regex(@"Customer rating (?<rating>\\d.\\d)/5.0");
...
MatchCollection matches = rx.Matches(X);
if (matches.Count > 0)
{
...
}

and it doesn't work. Matches.count is always 0.

PIEBALDconsult 7-Nov-14 9:59am

You can use "Improve question" to add that to the question. And please provide some examples.

Maciej Los · Answer 2 · 2014-11-07T04:53:00

Solution 2

Try this:

C#

string pattern = @"Customer rating (\d.\d)/5.0"

Regular Expression Language - Quick Reference[^]
Regular Expression Syntax[^]
http://www.regular-expressions.info/reference.html[^] - very good site with tons of examples!

Posted 7-Nov-14 4:53am

Maciej Los