Increment a value when conditions are met, otherwise set to zero - linq

Question

Given a list of strings, I'd like to create a list of the following object
class LineInfo
{
public string line { get; set; }
public bool isSearchMatch { get; set; }
public int searchMatchNumber { get; set; }
}
Where I'd like searchMatchNumber to have 1 for the 1st match, 2 for the 2nd, etc. Otherwise it can be zero
I set this up like so
IEnumerable<string> allLines; //pulled in from somewhere
IEnumerable<LineInfo> logInfoLines = allLines.Select((l, i) => new LineInfo
{
line = l,
isSearchMatch = l.IndexOf(search, StringComparison.OrdinalIgnoreCase) >= 0
});
How can I set searchMatchNumber?

Answer 1

LINQ queries should not cause side effects like this. If you'd add an OrderBy you'd get a different result. I wouldn't use LINQ for this, you could provide a method:
class LineInfo
{
public string line { get; set; }
public bool isSearchMatch { get; set; }
public int searchMatchNumber { get; set; }
public static IEnumerable<LineInfo> GetSearchResult(IEnumerable<string> allLines, string search)
{
int matchCounter = 0;
var lineInfoList = new List<LineInfo>();
foreach (string line in allLines)
{
bool isMatch = line.IndexOf(search, StringComparison.OrdinalIgnoreCase) >= 0;
var li = new LineInfo
{
line = line,
isSearchMatch = isMatch,
searchMatchNumber = isMatch ? ++matchCounter : -1 // or whatever
};
lineInfoList.Add(li);
}
return lineInfoList;
}
}