Question

I am starting to do a little development in C#, and I am stuck with a problem here. Usually I develop in Python where stuff like this is being implemented easily (at least for me), but I have no idea how to do that in C#:

I want to create a dictionary containing a list of dictionaries like the following using Generic Collections:

{ "alfred",  [ {"age", 20.0}, {"height_cm", 180.1} ],
  "barbara", [ {"age", 18.5}, {"height_cm", 167.3} ],
  "chris",   [ {"age", 39.0}, {"height_cm", 179.0} ]
}

I started with the following:

using System.Collections.Generic;
Dictionary<String, Dictionary<String, double>[]> persons;

But then I’d like to insert the three records from above at once into persons. I am stuck with syntax errors all the way.

Anyone have a solution for me?

Edit:

Thank you all – I didn’t expect to receive so many well thought answers in such a short time! You are great!

Answer 1

You could use dictionary initializes. Not as elegant as Python, but could live with:

var persons = new Dictionary<string, Dictionary<string, double>>
{
    { "alfred", new Dictionary<string, double> { { "age", 20.0 }, { "height_cm", 180.1 } } },
    { "barbara", new Dictionary<string, double> { { "age", 18.5 }, { "height_cm", 167.3 } } },
    { "chris", new Dictionary<string, double> { { "age", 39.0 }, { "height_cm", 179.0 } } }
};

And then:

persons["alfred"]["age"];

Also notice that you need Dictionary<string, Dictionary<string, double>> for this structure and not Dictionary<string, Dictionary<string, double>[]>.

Also working with such structure could be a little PITA and harm readability and compile-time type safety of the code.

In .NET it is preferred to work with strongly typed objects, like this:

public class Person
{
    public double Age { get; set; }
    public string Name { get; set; }
    public double HeightCm { get; set; }
}

and then:

var persons = new[]
{
    new Person { Name = "alfred", Age = 20.0, HeightCm = 180.1 },
    new Person { Name = "barbara", Age = 18.5, HeightCm = 180.1 },
    new Person { Name = "chris", Age = 39.0, HeightCm = 179.0 },
};

and then you could use LINQ to fetch whatever information you need:

double barbarasAge = 
    (from p in persons
     where p.Name == "barbara"
     select p.Age).First();

To be noted of course that using collections would not be as fast as a hashtable lookup but depending on your needs in terms of performance you could also live with that.