CODEWITHSUNDEEP
c#regexlinq
runfastman
runfastman

Reputation: 947

c# RegEx what line is the match on. Linq?

This one should be simple, but it is stumping me.

I have a Regex that could have a match. If it does, I want to know what line it is on. Is there a simple way to do this maybe with Linq without looping through each of the lines counting the characters?

  Regex rx = new Regex(myRegEx, RegexOptions.Compiled | RegexOptions.IgnoreCase);
  string[] docLines = File.ReadAllLines(myDocPath);
  // Find matches
  MatchCollection matches = rx.Matches(string.Join(Environment.NewLine, docLines));
  if(matches.Count > 0)
  {
    long loc = matches[0].Index;
    //Find the Line
  }

Upvotes: 1

Views: 135

Answers (3)

Jim Simson
Jim Simson

Reputation: 2862

Runfastman,

You can do this by using LINQ combined with an index like so:

using System.Linq;
using System.Text.RegularExpressions;
   
var rx = new Regex(myRegEx, RegexOptions.Compiled | RegexOptions.IgnoreCase);
var docLines = File.ReadAllLines(myDocPath);
var matchLine = docLines.Select((line, index) => new { line, index }).FirstOrDefault(l => rx.IsMatch(l.line));
if(matchLine != null) Console.WriteLine($@"Match line # = {matchLine.index}");

While it is true (as others have mentioned) that the compiler iterates over the lines to accomplish the task, I sense that the above is what you had in mind.

EDIT

In light of your comment that the target string could span multiple lines, I would do the following:

var rx = new Regex(myRegEx, RegexOptions.Compiled | RegexOptions.IgnoreCase);
//Read all text into a variable.
var docLines = File.ReadAllText(myDocPath);
//Check that there is, in fact, a match.
if(!rx.IsMatch(docLines)) return;
//Split your text blob by that match.
var rxSplit = rx.Split(docLines);
//Then count the number of line brakes before the match.
var startOfMatchLine = new Regex(@"(\n|\r\n?)").Matches(rxSplit[0]).Count;
//And print the result.
Console.WriteLine($@"{startOfMatchLine}");

Upvotes: 1

Nigrimmist
Nigrimmist

Reputation: 12378

You can find the line by using match.Value, for example :

Regex rx = new Regex("b", RegexOptions.Compiled | RegexOptions.IgnoreCase);
string[] docLines = new[] { "zzazz", "zzbzz", "zzczz", "zzzzz" };
// Find matches
MatchCollection matches = rx.Matches(string.Join(Environment.NewLine, docLines));
if (matches.Count > 0)
{
    string loc = matches[0].Value;
    //Find the Line
    var line = docLines.FirstOrDefault(x => x.Contains(loc));
}

Upvotes: -1

Caius Jard
Caius Jard

Reputation: 74605

You can match line by line:

  Regex rx = new Regex(myRegEx, RegexOptions.Compiled | RegexOptions.IgnoreCase);
  string[] docLines = File.ReadAllLines(myDocPath);
  // Find matches
  for(int x = 0; x < docLines.Length; x++){
    string line = docLines[x];
    if(rx.IsMatch(line))
      Console.Write($"Match on line {x}");
  }

Upvotes: 1

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