How to read and filter lines in text file Using C#

Question

1) I have a text file below like this.

Dilantha
code 65
po Bo 1255
colombo
sri lanka

joy
code 78
toronto
Canada

2) But I want the below result. ( I don't want the code 65 and code 78 parts)

Dilantha  colombo     sri lanka

joy       toronto     Canada

3) My requirment is, first I want to read the text file, then I want to filter the the result shown in 2 above.

Here's my Code. I'm using C#

    String line;
    String path = "c:/sample.txt";

    StreamReader sr = new StreamReader(path);
    while ((line = sr.ReadLine()) != null)
    {
        //display the readed lines in the text box
        disTextBox.AppendText(line+Environment.NewLine);
    }

this is example. i hav large lines of text file. plese help me to solve my problem. — Chamal, Feb 21 '11 at 18:15
Homework? Are all of the records in the file guaranteed to be in the same format? — Matt Mills, Feb 21 '11 at 18:15
You need to describe your format more specific. Is it always four lines text followed by one empty line? Is it always the second line that should be excluded? Or any line starting with "code" or any line starting with "code " followed by a number? — Albin Sunnanbo, Feb 21 '11 at 18:35
it is not same format. i hav edited the question to understand that. but it is always one set followed by one empty line. — Chamal, Feb 21 '11 at 18:50

score 2 · Answer 1 · answered Feb 21 '11 at 18:35

Use a StringBuilder to concatenate lines you read in
Use a Regex to skip over "code xx" lines
When you encounter a new line, print out what's in the StringBuilder
After you're done with the file, if you have anything left in your StringBuilder, print that out

static Regex codeRegex = new Regex("^code [\\d]+", RegexOptions.Compiled);

    static void Main(string[] args)
    {
        String line;
        String path = "c:/sample.txt";
        StringBuilder sb = new StringBuilder();

        StreamReader sr = new StreamReader(path);
        while ((line = sr.ReadLine()) != null)
        {
            line = line.Trim();

            if (codeRegex.IsMatch(line))
                continue;

            if (string.IsNullOrEmpty(line))
            {
                System.Console.Write(sb.ToString().Trim() + Environment.NewLine);
                sb.Clear();
            }
            else
            {
                sb.Append(line);
                sb.Append("\t");
            }
        }

        if (!string.IsNullOrEmpty(sb.ToString().Trim()))
            System.Console.Write(sb.ToString().Trim() + Environment.NewLine);
    }

score 2 · Accepted Answer · answered Feb 21 '11 at 19:12

How about create a function to return a list of strings for one group, then maybe a class to hold the values?

public static List<string> ReadGroup(TextReader tr)
{
    string line = tr.ReadLine();
    List<string> lines = new List<string>();
    while (line != null && line.Length > 0)
    {
        lines.Add(line);
    }

    // change this to line == null if you have groups with no lines
    if (lines.Count == 0) 
    {
        return null;
    }

    return lines;
}

Then you can access the lines by index in the list:

String line;
String path = "c:/sample.txt";

using (StreamReader sr = new StreamReader(path))
{
    while ((List<string> lines = ReadGroup(sr)) != null)
    {
        // you might want to check for lines.Count >= 4 if you will
        // have groups with fewer lines to provide a better error

        //display the readed lines in the text box
        disTextBox.AppendText(string.Format("{0}\t{1}\t{2}{3}",
            lines[0], lines[2], lines[3], Environment.NewLine);
    }
    sr.Close();
}

I notice that your first one has an extra line with "po Bo 1255". You need to know what format your file is to doanything meaningful. If the last two lines of a group are city and country, you need to use the count of lines. With a class:

class LineGroup // name whatever the data contains
{
    public string Name { get; set; }
    public string Code { get; set; }
    public string City { get; set; }
    public string Country { get; set; }

    public LineGroup(List<string> lines)
    {
        if (lines == null || lines.Count < 4)
        {
            throw new ApplicationException("LineGroup file format error: Each group must have at least 4 lines");
        }

        Name = lines[0];
        Code = lines[1];
        City = lines[lines.Count - 2];
        Country = lines[lines.Count - 1];
    }
}

And to process:

while ((List<string> lines = ReadGroup(sr) != null)
{
    LineGroup group = new LineGroup(lines);

    //display the readed lines in the text box
    disTextBox.AppendText(string.Format("{0}\t{1}\t{2}{3}",
        group.Name, group.City, group.Country, Environment.NewLine);
}

score 0 · Answer 3 · edited May 23 '17 at 11:55

0

Try it out this URL C# How to skip number of lines while reading text file using Stream Reader?

edited May 23 '17 at 11:55

Community

1
1

answered Feb 28 '11 at 19:04

dev

898
1
13
33

score 0 · Answer 4 · edited Oct 03 '19 at 02:53

0

You can use linq to filter data. If you have the parameter you want to filter by. Hope this can help you.

  string path = "Urlfile";
  List lineas = (from l in File.ReadAllLines(path)
                         where l.Contains("parametertofilter")
                         select l).ToList();

  //test filters with linq

edited Oct 03 '19 at 02:53

answered Oct 03 '19 at 02:31

Jose Francisco Castro

1

score 0 · Answer 5 · answered Feb 01 '12 at 22:22

Maybe you could start with this (or something else):

foreach (var line in File.ReadLines(myFilePath)) {
  if (line.Equals("code 65") || line.Equals("code 78")) 
    continue;

  // some logic to format lines into columns....
  // ....Append(string.Format("{0, -15}{1, -15}{2, -15}", lineValue1, lineValue2, lineValue3));
}

Only works since .NET 4.0.

How to read and filter lines in text file Using C#

5 Answers5