Question

I have 4 text files in one folder and a pattern.txt to compare these text files..In pattern.txt i have

insert
update
delete
drop

I need to compare this text file with those four text files and if these patterns matches any line in that text files i have to write those lines in another log file…i had read those files using linq..i need to compare those files and write in a text file with line number..here is my code

var foldercontent = Directory.GetFiles(pathA)
                    .Select(filename => File.ReadAllText(filename))
                    .Aggregate(new StringBuilder(),
                    (sb, s) => sb.Append(s).Append(Environment.NewLine),
                    sb => sb.ToString());

 var pattern =  File.ReadAllLines(pathB).Aggregate(new StringBuilder(),
                    (sb, s) => sb.Append(s).Append(Environment.NewLine),
                    sb => sb.ToString());

using (var dest = File.AppendText(Path.Combine(_logFolderPath, "log.txt")))
            {
      //dest.WriteLine("LineNo : " + counter.ToString() + " : " + "" + line);
            }

EDIT
I have already used c# to compare two text files but i need this in linq

while ((line = file.ReadLine()) != null)
{
if (line.IndexOf(line2, StringComparison.CurrentCultureIgnoreCase) != -1)
{
dest.WriteLine("LineNo : " + counter.ToString() + " : " + " " + line.TrimStart());
}
counter++;
}
file.BaseStream.Seek(0, SeekOrigin.Begin);
counter = 1; 

Answer 1

There might be a simpler solution, but this is at least working if you really want to use LINQ:

var foldercontent = Directory.GetFiles(pathA)
                    .Select(filename => new
                    {
                        Filename = filename,
                        Lines = File.ReadAllLines(filename)
                    })
                    .SelectMany(file => file.Lines.Select((line, idx) => new
                    {
                        LineNumber = idx + 1,
                        Text = line,
                        FileName = file.Filename
                    }));

var pattern = File.ReadAllLines(pathB);

var result = from fileLine in foldercontent
             where pattern.Any(p => fileLine.Text.IndexOf(p, StringComparison.CurrentCultureIgnoreCase) != -1)
             select fileLine;

foreach (var match in result)
{
    System.Diagnostics.Debug.WriteLine("File: {0} LineNo: {1}: Text: {2}", match.FileName, match.LineNumber, match.Text);
}

Or if you want, you can combine that into one LINQ query (but thats not very readable i think):

var result = from fileLine in (Directory.GetFiles(pathA)
                    .Select(filename => new
                    {
                        Filename = filename,
                        Lines = File.ReadAllLines(filename)
                    })
                    .SelectMany(file => file.Lines.Select((line, idx) => new
                    {
                        LineNumber = idx + 1,
                        Text = line,
                        FileName = file.Filename
                    })))
                where File.ReadAllLines(pathB).Any(p => fileLine.Text.IndexOf(p, StringComparison.CurrentCultureIgnoreCase) != -1)
                select fileLine;