C# Can StreamReader check current line number?

Question

I tried making a script that would read a TXT file line by line, and change labels depending on what is inside. Is there a way to check which line is being read?

Just add a counter in your program and increment it in your line by line reading loop — Alexey S. Larionov, May 25 '20 at 12:19
Currently trying that out. Kinda wanted to see if there was a less crude way — JEREDEK, May 25 '20 at 12:23
If someday someone would want to count number of words in a stream, it doesn't mean that `StreamReader` has to implement it. It does what it's designed to do - it just reads on demand — Alexey S. Larionov, May 25 '20 at 12:25
@JEREDEK thats no "crude way". What did you think is the best?every other solution will work the same way, the only difference? Any other developer had to do the work ;) — TinoZ, May 25 '20 at 12:26
You can try `File.ReadLines(...)` and *Linq*, e.g. `File.WriteAllLines(@"c:\myNewText.txt" File.ReadLines(@"c:\myText.txt").Select((line, number) => /*relevant code here*/));` — Dmitry Bychenko, May 25 '20 at 12:34

Charanjeet Singh · Accepted Answer · 2020-05-25T12:54:50.807

This example reads the contents of a text file, one line at a time, into a string using the ReadLine method of the StreamReader class and you can just check the line string and matches with your desire label and replace with that.

int counter = 0;  
string line;  

System.IO.StreamReader file = new System.IO.StreamReader(@"c:\test.txt");  
while((line = file.ReadLine()) != null)  
{  
    System.Console.WriteLine(line);  
    counter++;  
}  

file.Close();  
System.Console.WriteLine("There were {0} lines.", counter);  

System.Console.ReadLine();

OR

using System;
using System.IO;

public class Example
{
    public static void Main()
    {
        string fileName = @"C:\some\path\file.txt";

        using (StreamReader reader = new StreamReader(fileName))
        {
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                Console.WriteLine(line);
            }
        }
    }
}

Hope this will help you.

please, don't close reader explicitly - `file.Close();`, but wrap it into using: `using (file = new StreamReader(@"c:\test.txt")) {...}` — Dmitry Bychenko, May 25 '20 at 12:41
@DmitryBychenko , I have given him either option so now its his wish to go with. — Charanjeet Singh, May 25 '20 at 12:55

Dmitry Bychenko · Answer 2 · 2020-05-25T12:59:58.033

You can try querying file with a help of Linq:

  using System.IO;
  using System.Linq;

  ...

  var modifiedLines = File
    .ReadLines(@"c:\myInitialScript.txt") // read file line by line
    .Select((line, number) => {
       //TODO: relevant code here based on line and number

       // Demo: return number and then line itself
       return $"{number} : {line}";
     })
    // .ToArray() // uncomment if you want all (modified) lines as an array 
     ;

If you want write modified lines to a file:

  File.WriteAllLines(@"c:\MyModifiedScript.txt", modifiedLines);

If you insist on StreamReader, you can implement a for loop:

  using (StreamReader reader = new StreamReader("c:\myInitialScript.txt")) {
    for ((string line, int number) record = (reader.ReadLine(), 0); 
          record.line != null; 
          record = (reader.ReadLine(), ++record.number)) {
      //TODO: relevant code here
      //     record.line - line itself
      //   record.number - its number (zero based)
    }
  }

C# Can StreamReader check current line number?

2 Answers2