Efficient way to store a set of list of string in C#

Question

I want to know which is the most efficient way to store a set of list of strings in C#.

Background

My goal is to store information about "properties" like Hold(object) or Location(x,y,object). To do this I have a dictionary that map the property name to a "set of values".

For example, suppose I have a "location" set for the "location" property with these values

location -> ["1","2","robot1"]
            ["2","3","robot2"]
            ["2","5","key1"]

I want to perform query like

DB["location"].Contains(["1","2","robot1"])

I don't know if it is possible but it is to give you an idea of what I need. :)

What I have done

I have to modify and access these data frequently so I opted for an HashSet. But I have two main options:

The first is to use something like HashSet<string[]>. The problem is I think that HashSet cannot find duplicates because the standard behavior is to compare arrays by reference. For the same reason I don't know a good way to solve the "check if a [a,b,c] is contained in the set" problem.
The second is to use something like HashSet<List<string>>. But I don't need a List to store a simple set of tuple. It seems to me too much for a simple job like that.

An alternative is to write my own class to store "arguments" but I don't want to do this if something exists in the standard library. :)

Thanks :)

Is there a reason for why you would like to use strings, rather than just creating classes to represent these collection of properties? — Porkbutts
– Porkbutts, Commented May 24, 2013 at 16:27
@Porkbutts Because I will know the properties only at runtime. I parse property definition from a file (similar to PDDL so I need something that can handle every possible definition. I'm using strings because I get them directly from the file. — Davide Aversa
– Davide Aversa, Commented May 24, 2013 at 17:01
Instead of having a HashSet of type string[], why not create a class that encapsulates the string[] but overrides HashCode/Equals using, say, the concatenation of the strings (with some delimiter). That will provide you with the desired functionality I believe. E.g. Hashcode(["1", "2", "robot1"]) == Hashcode("1 2 robot1") or something similar. (I say use a delimiter so you don't have situations like ["1", "2robot1"] == ["1", "2", "robot1"] — Porkbutts
– Porkbutts, Commented May 24, 2013 at 18:06

Reed Copsey · Accepted Answer · 2013-05-24 16:27:11Z

3

An alternative is to write my own class to store "arguments" but I don't want to do this if something exists in the standard library. :)

This would actually be my preference. While it's a bit of work to write this up, having an actual type to hold the values provides the ability to build the equality directly into the type, and makes its usage very explicit.

In your case, you could store 2 ints and a string instead of 3 strings, etc. More importantly, the int and string values can be named appropriately, which in turn makes your code far more readable and understandable.

answered May 24, 2013 at 16:27

Reed Copsey

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1 Comment

Davide Aversa Over a year ago

This is the way I'm going. Unfortunately I have to "generalize" because I will know the properties type only at runtime (I parse them from a file).

David · Accepted Answer · 2013-05-24 16:36:57Z

Use HashSet and Tuple might be a choice

HashSet<Tuple<int, int, string>> collections;

and if you prefer using all strings:

HashSet<Tuple<string, string, string>> collections;

And for equality of Tuple, you might find this MSDN link useful. No matter which form you like, you can use below example as a reference:

Tuple<string, double, int>[] scores = 
                  { Tuple.Create("Ed", 78.8, 8),
                    Tuple.Create("Abbey", 92.1, 9), 
                    Tuple.Create("Ed", 71.2, 9),
                    Tuple.Create("Sam", 91.7, 8), 
                    Tuple.Create("Ed", 71.2, 5),
                    Tuple.Create("Penelope", 82.9, 8),
                    Tuple.Create("Ed", 71.2, 9),
                    Tuple.Create("Judith", 84.3, 9) };

  // Test each tuple object for equality with every other tuple. 
  for (int ctr = 0; ctr < scores.Length; ctr++)
  {
     var currentTuple = scores[ctr];
     for (int ctr2 = ctr + 1; ctr2 < scores.Length; ctr2++)
        Console.WriteLine("{0} = {1}: {2}", currentTuple, scores[ctr2], 
                                            currentTuple.Equals(scores[ctr2]));      

     Console.WriteLine();
  }   
}

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