C# Regex Formatting String without Input string

Question

I have the following Regex that is being used to matching incoming packets:

public static class ProtobufConstants
{
    public static Regex ContentTypeNameRegex => new Regex("application/protobuf; proto=(.*?)");
}

I also need to write outgoing packets strings in the same format, i.e. create strings similar to "application/protobuf; proto=mynamespace.class1" ideally by using the same regex definition new Regex("application/protobuf; proto=(.*?)");.

To keep this code in one place, is it possible to use this regex template and replace the (.*?) parameter with a string (as per above example i would like to substitute "mynamespace.class1").

I see there is a Regex.Replace(string input, string replacement) but given the above ContentTypeNameRegex already has the format defined I don't have an input per se, I just want to format - not sure what to put here, if anything.

Is it possible to use in this manner, or do i need to revert to string.Format?

public static Regex ContentTypeNameRegex(string protoPattern = ".*?")? — 41686d6564
– 41686d6564, Commented Oct 13, 2018 at 20:43
Hi Ahmed thanks for the quick reply, have updated my question as may not have been clear — morleyc
– morleyc, Commented Oct 13, 2018 at 20:55

41686d6564 · Accepted Answer · 2018-10-13 21:05:43Z

2

If you just want to replace the matched group with something else, you can change your pattern to:

(application/protobuf; proto=)(.*?)

That way, you can replace it by doing something like:

Regex re = ContentTypeNameRegex;
string replacement = "mynamespace.class1";
re.Replace(input, "$1" + replacement);

edited Oct 13, 2018 at 21:05

answered Oct 13, 2018 at 20:45

41686d6564

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ΩmegaMan · Accepted Answer · 2018-11-07 19:54:58Z

0

Use Regex.Replace but use the match evaluator to handle your formatting needs. Here is an example which simply replaces a slash with a dash and visa versa, based on what has been matched.

var text = "001-34/323";

Regex.Replace(text, "[-/]", me => { return me.Value == "-" ? "/" : "-";   })

Result

001/34-323

You can do the same with your input, to decide to change it or send it on as is.

answered Nov 7, 2018 at 19:54

ΩmegaMan

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