search text file using c# and display the line number and the complete line that contains the search keyword

This is a slight modification from: http://msdn.microsoft.com/en-us/library/aa287535%28VS.71%29.aspx

int counter = 0;
string line;

// Read the file and display it line by line.
System.IO.StreamReader file = new System.IO.StreamReader("c:\\test.txt");
while((line = file.ReadLine()) != null)
{
    if ( line.Contains("word") )
    {
        Console.WriteLine (counter.ToString() + ": " + line);
    }

   counter++;
}

file.Close();

Bit late to the game on this one, but happened across this post and thought I'd add an alternative answer.

foreach (var match in File.ReadLines(@"c:\LogFile.txt")
                          .Select((text, index) => new { text, lineNumber = index+ 1 })
                          .Where(x => x.text.Contains("SEARCHWORD")))
{
    Console.WriteLine("{0}: {1}", match.lineNumber, match.text);
}

This uses:

• File.ReadLines, which eliminates the need for a StreamReader, and it also plays nicely with LINQ's Where clause to return a filtered set of lines from a file.

• The overload of Enumerable.Select that returns each element's index, which you can then add 1 to, to get the line number for the matching line.

Sample Input:

just a sample line
another sample line
first matching SEARCHWORD line
not a match
...here's aSEARCHWORDmatch
SEARCHWORD123
asdfasdfasdf

Output:

3: first matching SEARCHWORD line
5: ...here's aSEARCHWORDmatch
6: SEARCHWORD123