C# Dictionary Composition

Question

Let's say I have an arbitray list of A

class A
{
string K {get;set;}
string V {get;set;}
}

...
List<A> theList = ...

Is there an easy way to compose a dictionary from theList? (something like the following)

Dictionary<string, string> dict = magic(x => x.K, x => x.V, theList)

I don't want to write the following code:

var d = new Dictionary<string, string>
foreach(var blah in theList)
    d[blah.K] = blah.V

Answer 1

If the list is an IEnumerable<A> then most definitely. You would use the ToDictionary extension method on the Enumerable class in the System.Linq namespace in .NET 3.5 and beyond like so:

Dictionary<string, string> d = theList.ToDictionary(a => a.K, a => a.V);

Which will give you a Dictionary where the key is the value in the K property, and the value is the value in the V property.

Answer 2

There's this: Enumerable.ToDictionary.

You use it like this:

Dictionary<string, string> dict = theList.ToDictionary(e => e.K, e => e.V);

Answer 3

Dictionary<string,string> dict = new Dictionary<string,string>();

theList.ForEach( param => dict[param.K] = param.V );

A little shorter, but still basically a for-each loop. I like the ToDictionary() solution better.

Answer 4

Enumarable.ToDictionary<TSource,TKey> is what you are looking for:

theList.ToDictionary(x => x.K, x => x.V);

Answer 5

var dict = theList.Cast<A>().ToDictionary(a => a.K, a => a.V);

Answer 6

Dictionary<string, string> dict = theList.ToDictionary( x => x.K , x=> x.V);