LINQ Searching ordered list and appending occurence number - linq

Question

I have the following custom class
public class Album
{
public string PhotoName { get; set; }
public string Location { get; set; }
public DateTime DateTime { get; set; }
}
and I have the following string:
#"photo.jpg, Warsaw, 2013-09-05 14:08:15
john.png, London, 2015-06-20 15:13:22
myFriends.png, Warsaw, 2013-09-05 14:07:13
Eiffel.jpg, Paris, 2015-07-23 08:03:02
pisatower.jpg, Paris, 2015-07-22 23:59:59
BOB.jpg, London, 2015-08-05 00:02:03"
and I need to write a function that will append the order number beside the Location based on the timestamp thus the resulting StringBuilder must be
Warsaw01.jpg
London01.jpg
Warsaw02.jpg
Paris01.jpg
Paris02.jpg
London02.jpg
What I have done so far?
I have a List of that type that I sorted by Location then by DateTime
List<Album> SortedList = list
.OrderBy(o => o.Location)
.ThenBy(o => o.DateTime)
.ToList();
now I need to have a StringBuilder that will append the index number beside the location.
This is my complete method with the part and I am stuck on how should I search the ordered list. Question is: how can I write the LINQ for searching through the list?:
public static string Solution(string S)
{
string[] group = S.Split("\r\n");
List<Album> list = new List<Album>();
StringBuilder sb = new StringBuilder();
//added each line of the string to list
foreach (string g in group)
{
string[] album = g.Split(',');
Album a = new Album();
a.PhotoName = album[0];
a.Location = album[1];
a.DateTime = DateTime.Parse(album[2]);
list.Add(a);
}
//ordered the list
List<Album> SortedList = list.OrderBy(o => o.Location).ThenBy(o => o.DateTime).ToList();
//then foreach line, append index number by searching through the list
foreach (string g in group)
{
string[] album = g.Split(',');
Album a = new Album();
a.PhotoName = album[0];
string[] photodetails = a.PhotoName.Split('.');
a.Location = album[1];
a.DateTime = DateTime.Parse(album[2]);
//this is the part where I must figure out how to build the string. I am stuck here
// var query = SortedList.IndexOf(list.SingleOrDefault(i => i.DateTime == a.DateTime));
sb.AppendLine(a.Location + query + "." + photodetails[1]);
}
string res = sb.ToString();
return res;
}
Appreciate the responses.
Update Warsaw2 must appear before Warsaw1 since the timestamp of Warsaw2 is later than Warsaw1
Warsaw02.jpg
London01.jpg
Warsaw01.jpg
Paris01.jpg
Paris02.jpg
London02.jpg

Answer 1

I have just added a order in the Album class
public class Album
{
public string PhotoName { get; set; }
public string Location { get; set; }
public DateTime DateTime { get; set; }
public int Order { get; set; }
}
public static string Solution(string S)
{
string[] stringSeparators = new string[] { "\r\n" };
string[] group = S.Split(stringSeparators, StringSplitOptions.None);
List<Album> list = new List<Album>();
StringBuilder sb = new StringBuilder();
//added each line of the string to list
for (int i = 0; i < group.Length; i++)
{
string[] album = group[i].Split(',');
Album a = new Album();
a.PhotoName = album[0];
a.Location = album[1];
a.DateTime = DateTime.Parse(album[2]);
a.Order = i;
list.Add(a);
}
//ordered the list
var groupedByLocation = list.GroupBy(o => o.Location).ToList();
for (int i = 0; i < groupedByLocation.Count; i++)
{
int indexValue = 01;
foreach (var item in groupedByLocation[i])
{
item.PhotoName = string.Format("{0}{1}.jpg", groupedByLocation[i].Key, indexValue);
indexValue++;
}
}
//then foreach line, append index number by searching through the list
var locations = groupedByLocation
.SelectMany(g => g.Select(h => h))
.ToList()
.OrderBy(y => y.Order)
.Select(g => g.PhotoName);
return string.Join("\r\n", locations);
}

Answer 2

Just for the fun - an alternative approach:
For the task at hand, there's no need to have an Album class, a list and two loops.
We can go over the lines once, and use a dictionary to hold the counters for us.
class PhotoLocationsCounter
{
private readonly Dictionary<string, int> locationsCounter = new Dictionary<string, int>();
public string GetLocationsWithCounters(string source)
{
string[] lines = source.Split(new[] { '\n' }, StringSplitOptions.RemoveEmptyEntries);
var locations = lines.Select(this.LineToLocationWithCounter);
return string.Join("\n", locations);
}
private string LineToLocationWithCounter(string line)
{
string[] album = line.Split(',');
var location = album[1].Trim();
var ext = album[0].Split('.')[1];
var counter = this.GetAndIncreaseLocationCounter(location);
return $"{location}{counter.ToString("D2")}.{ext}";
}
private int GetAndIncreaseLocationCounter(string location)
{
if (!this.locationsCounter.TryGetValue(location, out int counter))
{
this.locationsCounter.Add(location, 0);
}
return ++this.locationsCounter[location];
}
}
And you call it:
string data = #"photo.jpg, Warsaw, 2013-09-05 14:08:15
john.png, London, 2015-06-20 15:13:22
myFriends.png, Warsaw, 2013-09-05 14:07:13
Eiffel.jpg, Paris, 2015-07-23 08:03:02
pisatower.jpg, Paris, 2015-07-22 23:59:59
BOB.jpg, London, 2015-08-05 00:02:03";
var locations = new PhotoLocationsCounter().GetLocationsWithCounters(data);