如何通过分隔符和多个分组来分割字符串并在Linq中对它们进行计数？

Question

I have a LogData List and which is designed like below.

public class LogDataEntity
{
   public string IndexPattern;
   public int Type;
   public LogDataEntity(string pattern , int type)
   {
         IndexPattern = pattern;
         Type = type;
   }
}


List<LogDataEntity> list = new List<LogDataEntity>();
list.add(new LogDataEntity("1,2,9,10", 2));    
list.add(new LogDataEntity("1,10", 1));
list.add(new LogDataEntity("1,2,3", 2));
list.add(new LogDataEntity("3,9,10", 3));
list.add(new LogDataEntity("9,10", 2));
list.add(new LogDataEntity("9,10", 2));

And i want the result like below.

 [Index]   [Type]    [Count]
   10    :   2          3      
   9     :   2          3     
   1     :   2          2      
   3     :   1          2     
   2     :   2          2 
   3     :   3          1
   9     :   3          1
   10    :   3          1
   1     :   1          1

I want to group by and count not only splited string(indexpattern) but also type too. And i want to count and show them by OrderByDescending(Count).

I think There is multiple group by. How should i do this with Linq?

Answer 1

You can use SelectMany to create list of (Index, Type) pairs, then group by and count to do the rest:

var pairs = data.SelectMany(x => x.IndexPattern
                                  .Split(",")
                                  .Select(y => new {Index = y, Type = x.Type});

var res = from p in pairs
          group p by new { p.Index, p.Type } into grp
          select new {
            Index = grp.Key.Index,
                    grp.Key.Type,
                    grp.Count()
          };

(An order by clause can be added before the final Select as required.)

Answer 2

You've, probably, stuck in SelectMany ; all the other commands are quite evident:

var result = list
  .SelectMany(record => record 
     .IndexPattern
     .Split(',')
     .Select(item => {
        index = item,
        type = record.Type, 
      }))
   .GroupBy(item => item)
   .OrderByDescending(chunk => chunk.Count())
   .Select(chunk => $"{chunk.index,-10} : {chunk.type,-10} {chunk.Count()}");  

Console.WriteLine(string.Join(Environment.NewLine, result));

Answer 3

This is improve version or previous answers.

var pairs = Logs.SelectMany(x => x.IndexPattern.Split(',').Select(y => new { 
Index = y, Type= x.Type }));

var pairs2 = (from p in pairs group p by p into grp select new { Index = 
grp.Key.Index, Reason = grp.Key.Type, Count = grp.Count() }
            ).OrderByDescending(p => p.Count);


foreach (var i  in pairs2) 
{

   //print with i
}