Question

I want to separate an array of my custom object into several arrays, based on the values of their two properties. The struct looks like this:

struct MyStruct {

    public string Person {
        get;
        set;
    }
    public string Command {
        get;
        set;
    }
}

Now, if I have an array with a few objects:

{Person1, cmd1}
{Person1, cmd3}
{Person2, cmd3}
{Person3, cmd2}
{Person2, cmd4}

I want to be able to place them into one array for each person, that lists all of the commands for that person:

{Person1: cmd1, cmd3}
{Person2: cmd3, cmd4}
{Person3: cmd2}

I hope I’ve made it clear with my descriptions. I would assume that there is an elegant way to do this with LINQ, but I have no idea where to start.

Answer 1

IEnumerable<MyStruct> sequence = ...

var query = sequence.GroupBy(s => s.Person)
                    .Select(g => new 
                                 { 
                                    Person = g.Key,
                                    Commands = g.Select(s => s.Command).ToArray() 
                                 })
                    .ToArray();

A similar query in query syntax:

var query = from s in sequence
            group s.Command by s.Person into g
            select new { Person = g.Key, Commands = g.ToArray() };

var queryArray = query.ToArray();

Do note that you asked for an array of arrays, but the result here is an array of an anonymous type, one of whose members is an array of strings.

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On an another note, it’s usually not recommended to create mutable structs.