Question

I have an in-memory ‘table’ that might looks something like this:

Favorite#  Name        Profession ---------  ----------  ------------------ 3          Names.Adam  Profession.Baker 9          Names.Bob   Profession.Teacher 7          Names.Carl  Profession.Coder 7          Names.Dave  Profession.Miner 5          Names.Fred  Profession.Teacher 

And what I want to do, is do quick and efficient lookups, using any of the 3 fields. In other words, I want:

• myTable[3] and myTable[Names.Adam] and myTable[Professions.Baker] to all return {3,Names.Adam,Profession.Baker}
• myTable[Profession.Teacher] to return both {9,Names.Bob,Profession.Teacher} and {5,Names.Fred,Profession.Teacher}.

The table is built during runtime, according to the actions of the user, and cannot be stored in a database since it is used in sections in which database connectivity cannot be guaranteed.

Right now, I ‘simply’ (hah!) store this using 3 uber-Dictionaries, each keyed using one of the columns (FavoriteNumber, Name, Profession), and each value in the uber-Dictionaries holding 2 Dictionaries which are themselves keyed with each of the remaining columns (so the values in the ‘Name’ uber-dictionary are of the type Dictionary<FavoriteNumber,Profession[]> and Dictionary<Profession, FavoriteNumber[]>

This requires 2 lookups in 2 Dictionaries, and another traverse of an array (which usually holds 1 or 2 elements.)

Can anyone suggest a better way to do this? I don’t mind spending extra memory, since the table is likely to be small (no more than 20 entries) but I’m willing to sacrifice a little CPU to make it more readily maintainable code…

Answer 1

Not really however using a dictionary, but if you create a collection of classes like this

class Person {     public int FavoriteNumber;     public string Name;     public string Profession; } 

you can use LINQ to search the collections.

IList<Person> people = /* my collection */; var selectedPeople = people.Where(p => p.FavoriteNumber = 3); var selectedPeople2 = people.Where(p => p.Name == 'Bob'); var selectedPeople3 = people.Where(p => p.Profession = 'Teacher'); 

or if you prefer the normal LINQ syntax

var selectedPeople4 = from p in people                       where p.Name == 'Bob'                       select p; 

Each of these selectedPeople variables will be typed as IEnumerable<Person> and you can use a loop to search through them.