c# list of strings > sort by regex ?

Question

I am quite new to c# but I can't resolve this issue ( most probably a simple one ).

I have 2 List that contain strings of error logs. ( Let me know if it's better to use an array of strings )

/* Example of list from host 1
2017-06-29 02:25:54.309 BST,ERROR,.......
2017-06-29 02:25:54.357 BST,ERROR,.......
2017-06-29 02:25:54.495 BST,ERROR,.......
2017-06-29 02:30:57.183 BST,ERROR,.......
2017-06-29 03:07:12.078 BST,ERROR,.......
2017-06-29 05:07:13.256 BST,ERROR,.......
2017-06-29 05:14:14.717 BST,ERROR,.......
2017-06-29 05:16:23.954 BST,ERROR,.......
2017-06-29 08:12:16.418 BST,ERROR,.......
2017-06-29 08:37:23.574 BST,ERROR,.......
2017-06-29 09:07:11.569 BST,ERROR,....... */
List<string> filteredLogFileC1 = filterLog(hostNameC1); //filterLog returns a List<string>

/* Example of list from host 2
2017-06-29 00:43:43.781 BST,ERROR,.......
2017-06-29 00:43:44.446 BST,ERROR,.......
2017-06-29 00:43:44.885 BST,ERROR,.......
2017-06-29 00:43:45.378 BST,ERROR,.......
2017-06-29 00:43:45.940 BST,ERROR,.......
2017-06-29 00:43:46.584 BST,ERROR,.......
2017-06-29 00:43:47.141 BST,ERROR,....... */ 
List<string> filteredLogFileC2 = filterLog(hostNameC2); //filterLog returns a List<string>

// Combine the 2 lists into one (the below practice might not be the best one but its working and I am happy at the moment :) )

/*
... Combined list
2017-06-29 08:12:16.418 BST,ERROR,.......
2017-06-29 08:37:23.574 BST,ERROR,.......
2017-06-29 09:07:11.569 BST,ERROR,....... 
2017-06-29 00:43:43.781 BST,ERROR,.......
2017-06-29 00:43:44.446 BST,ERROR,.......
2017-06-29 00:43:44.885 BST,ERROR,.......
...
*/
foreach (string line in filteredLogFileC2) filteredLogFileC1.Add(line);


// I need to sort the filteredLogFileC1 list by date.
// Below I have a regex that I've put together but I don't know how I can use it 

Regex sortReg = new Regex(@"(\d{4}-\d{2}-\d{2}) (\d{2}:\d{2}:\d{2}.\d{3})");

Issue: filteredLogFileC1.OrderBy( ???sortReg??? )

Thank you for your suggestions.

Answer 1

Sort method would work for your case, but since it is not stable based on the docs (doesn't preserve original order in case of similar dates), I Recommend using OrderBy (which is stable):

filteredLogFileC1 = filteredLogFileC1.OrderBy(dt => dt).ToList();

In the above lambda (dt => dt) , you're saying: Sort the strings by their own values.

If that wasn't a string but a data structure that have a Date Field for example, you could say ( dt => dt.Date ) in order to sort by that field (just to clear the lambda which seems to be confusing you a little bit).

Answer 2

I tried this before and didn't work:

filteredLogFileC1.OrderBy(x => x)); // maybe I should have stored this into a new list ?
File.WriteAllLines(localPath + "combined.log", filteredLogFileC1);

---

This way it works for me and generates the output also:

File.WriteAllLines(localPath + "combined.log", filteredLogFileC1.OrderBy(x => x));

Answer 3

If I understood your task right - this can be:

filteredLogFileC1.Union(filteredLogFileC2).OrderBy(l => sortReg.Match(l).Value)

The code result is IEnumerable. You can use an extension method .ToList() to converti it. Also, if Regex fails to match - the result value will be an empty string else it will be the desired substring.

Answer 4

You should create date from your string, and sort by date

var matchedLines = filteredLogFileC1.Where(x => sortReg.IsMatch(x)).OrderBy(x => DateTime.ParseExact(sortReg.Match(x).Value, "yyyy-MM-dd HH:mm:ss.fff", null)); // lines that match date pattern, ordered by date value
var unMatchedLines = filteredLogFileC1.Where(x => !sortReg.IsMatch(x)); // Lines that do not match date pattern. Can be added at the top or bottom