Question

I want to get random number of lines(let’s say 2 ) group by Code from text file.

for e.g.

4581511:         50.27:        AT
1223522:         86.99:        AT
7456117:         68.59:        QW
5261789:         39.17:        QW
…..
…..

Text File

bookNumber      Price     Code
4581511:         50.27:        AT
7841522:         26.13:        AT
7353532:         96.13:        AT
1223522:         86.99:        AT
8415621:         89.70:        IT
8411442:         82.42:        IT
4555577:         19.14:        IT
7655577:         65.45:        IT
2754831:         35.44:        DR
1364449:         82.47:        DR
4545454:         45.65:        DR
8795457:         78.36:        DR
5261789:         39.17:        QW
7845522:         10.42:        QW
7456117:         68.59:        QW
4346129:         23.78:        QW

I got this far and I am geting 2 lines which are not random but in sequence

Code

static IEnumerable<string> ReadLines(string path)
    {

        using (var file = File.OpenText(path))
        {
            string line;
            while ((line = file.ReadLine()) != null)
            {
                if (line.Contains(":"))
                {
                    yield return line;
                }
            }
        }
    } 

    public static IEnumerable<string> GetrandomLines()
    {

        string filepath = "file location";
        var readTextFile = ReadLines(filepath);
        var codeGroup = readTextFile.GroupBy(line => line.Substring(line.Length - 2))
                          .Select(g => new
                          {
                            value = g.Key,
                            count = g.Count()
                           });


        foreach (var item in codeGroup)
        {
            Random randomLineGenerator = new Random(DateTime.Now.Millisecond);
             var randomLines = (from x in readTextFile
                                where x.Substring(x.Length - 2) == item.value
                                select x).Skip(randomLineGenerator.Next(0, item.count)).Take(2);
             foreach (var line in randomLines)
             {
                 yield return line;
             }
        }

    }

Any Ideas?

Thanks

Answer 1

Guid version, the random values can’t be the same.

public static IEnumerable<string> GetrandomLines2(string filePath, int lines)
{
    return ReadLines(filePath)
        .GroupBy(line => line.Substring(line.Length - 2))
        .SelectMany(s => s.OrderBy(g => Guid.NewGuid()).Take(lines));
}

Random version, the two random values may be the same.

public static IEnumerable<string> GetTwoRandomLines(string filePath)
{
    var codeGroup = ReadLines(filePath)
        .GroupBy(line => line.Substring(line.Length - 2));

    Random rnd = new Random(DateTime.Now.Millisecond);

    foreach (var item in codeGroup)
    {
        yield return item.Skip(rnd.Next(item.Count())).FirstOrDefault();
        yield return item.Skip(rnd.Next(item.Count())).FirstOrDefault();
    }
}