Regex group string replace issue

Question

The target string is "A + A_RT + B*A+AA". I want to replace A with B and B with A. But I don't want to replace A_RT to B_RT or AA to BB. The expected result is "B + A_RT + A*B+AA". How can I do this in C#? Thanks.

Currently I use the following codes, but it will replace A_RT to B_RT...

IDictionary<string, string> map = new Dictionary<string, string>()
                                  {
                                      {"A","B"},
                                      {"B","A"},
                                  };

string str = "A + A_RT + B*A+AA";
var regex = new Regex(String.Join("|", map.Keys));
var newStr = regex.Replace(str, m => map[m.Value]);

You need to use look behind and look ahead to check whether there is any valid character for a name. — nhahtdh
– nhahtdh, Commented Oct 12, 2012 at 2:44
Append (?<!\w) before and (?!\w) after the regex to see whether it works or not. — nhahtdh
– nhahtdh, Commented Oct 12, 2012 at 2:48

nhahtdh · Accepted Answer · 2012-10-12 09:56:34Z

2

I changed the regex to var regex = new Regex(@"\bA\b|\bB\b"), then it can work.

edited Oct 12, 2012 at 9:56

nhahtdh

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answered Oct 12, 2012 at 3:23

Denny

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Comments

Rob · Accepted Answer · 2012-10-12 02:59:12Z

0

I'm not particularly good at regex patterns, so there is probably a better way to do this. But the pattern

@"([a-zA-Z_]+)"

was able to grab all your variable tokens as match results.

answered Oct 12, 2012 at 2:59

Rob

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Comments

Petr Behenský · Accepted Answer · 2012-10-12 10:14:44Z

0

Use var regex = new Regex(String.Format("\\b[{0}]\\b",String.Join("", map.Keys)));

answered Oct 12, 2012 at 10:14

Petr Behenský

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