Question

I have a List containing a bunch of strings that can occur more than once. I would like to take this list and build a dictionary of the list items as the key and the count of their occurrences as the value.

Example:

List<string> stuff = new List<string>(); stuff.Add( 'Peanut Butter' ); stuff.Add( 'Jam' ); stuff.Add( 'Food' ); stuff.Add( 'Snacks' ); stuff.Add( 'Philosophy' ); stuff.Add( 'Peanut Butter' ); stuff.Add( 'Jam' ); stuff.Add( 'Food' ); 

and the result would be a Dictionary containing:

'Peanut Butter', 2 'Jam', 2 'Food', 2 'Snacks', 1 'Philosophy', 1 

I have a way to do this, but it doesn’t seem like I’m utilizing the good stuff in C# 3.0

public Dictionary<string, int> CountStuff( IList<string> stuffList ) {     Dictionary<string, int> stuffCount = new Dictionary<string, int>();      foreach (string stuff in stuffList) {         //initialize or increment the count for this item         if (stuffCount.ContainsKey( stuff )) {             stuffCount[stuff]++;         } else {             stuffCount.Add( stuff, 1 );         }     }      return stuffCount; } 

Answer 1

You can use the group clause in C# to do this.

List<string> stuff = new List<string>(); ...  var groups =      from s in stuff     group s by s into g     select new {          Stuff = g.Key,          Count = g.Count()      }; 

You can call the extension methods directly as well if you want:

var groups = stuff     .GroupBy(s => s)     .Select(s => new {          Stuff = s.Key,          Count = s.Count()      }); 

From here it’s a short hop to place it into a Dictionary<string, int>:

var dictionary = groups.ToDictionary(g => g.Stuff, g => g.Count);