Recipe 8.9 Counting Lines of Text

Problem

You need to count lines of text within a string or within a file.

Solution

Read in the entire file and count the number of linefeeds, as shown in the following method:

 using System; using System.Text.RegularExpressions; using System.IO; public static long LineCount(string source, bool isFileName) {     if (source != null)     {         string text = source;         if (isFileName)         {             FileStream FS = new FileStream(source, FileMode.Open,                                           FileAccess.Read, FileShare.Read);             StreamReader SR = new StreamReader(FS);             text = SR.ReadToEnd( );             SR.Close( );             FS.Close( );         }         Regex RE = new Regex("\n", RegexOptions.Multiline);         MatchCollection theMatches = RE.Matches(text);         // Needed for files with zero length         //   Note that a string will always have a line terminator          //        and thus will always have a length of 1 or more         if (isFileName)         {             return (theMatches.Count);         }         else         {             return (theMatches.Count) + 1;         }     }     else     {         // Handle a null source here         return (0);     } } 

An alternative version of this method uses the StreamReader.ReadLine method to count lines in a file and a regular expression to count lines in a string:

 public static long LineCount2(string source, bool isFileName) {     if (source != null)     {         string text = source;         long numOfLines = 0;         if (isFileName)         {             FileStream FS = new FileStream(source, FileMode.Open,                                           FileAccess.Read, FileShare.Read);             StreamReader SR = new StreamReader(FS);             while (text != null)             {                 text = SR.ReadLine( );                 if (text != null)                 {                     ++numOfLines;                 }             }             SR.Close( );             FS.Close( );             return (numOfLines);         }         else         {             Regex RE = new Regex("\n", RegexOptions.Multiline);             MatchCollection theMatches = RE.Matches(text);             return (theMatches.Count + 1);         }     }     else     {         // Handle a null source here         return (0);     } } 

The following method counts the lines within a specified text file and a specified string:

 public static void TestLineCount( ) {     // Count the lines within the file TestFile.txt     LineCount(@"C:\TestFile.txt", true);     // Count the lines within a string     // Notice that a \r\n characters start a new line      //    as well as just the \n character     LineCount("Line1\r\nLine2\r\nLine3\nLine4", false); } 

Discussion

Every line ends with a special character. For Windows files, the line terminating characters are a carriage return followed by a linefeed . This sequence of characters is described by the regular expression pattern \r\n . Unix files terminate their lines with just the linefeed character ( \n ). The regular expression " \n " is the lowest common denominator for both sets of line-terminating characters. Consequently, this method runs a regular expression that looks for the pattern " \n " in a string or file.

Macintosh files usually end with a carriage-return character ( \r ). To count the number of lines in this type of file, the regular expression should be changed to the following in the constructor of the Regex object:

 Regex RE = new Regex("\r", RegexOptions.Multiline); 

Simply running this regular expression against a string returns the number of lines minus one because the last line does not have a line-terminating character. To account for this, one is added to the final count of linefeeds in the string.

The LineCount method accepts two parameters. The first is a string that either contains the actual text that will have its lines counted or the path and name of a text file whose lines are to be counted. The second parameter, isFileName , determines whether the first parameter ( source ) is a string or a file path. If this parameter is true , the source parameter is a file path; otherwise , it is simply a string.

See Also

See the ".NET Framework Regular Expressions," "FileStream Class," and "StreamReader Class" topics in the MSDN documentation.