Map one dictionary to another using Linq

Question

Is there an elegant way to map one Dictionary to another using Linq in the .NET framework?

This can be accomplished via enumerating with foreach:

var d1 = new Dictionary<string, string>() {
    { "One", "1" },
    { "Two", "2" }
};

// map dictionary 1 to dictionary 2 without LINQ
var d2 = new Dictionary<string, int>();
foreach(var kvp in d1) {
    d2.Add(kvp.Value, int.Parse(kvp.Value));
}

...but I'm looking for some way to accomplish with LINQ:

// DOES NOT WORK
Dictionary<string, int> d2 =
    d1.Select(kvp => {
        return new KeyValuePair<string, int>(kvp.Key, int.Parse(kvp.Value));
    })

Answer 1

Just use ToDictionary extension method from System.Linq namespace

var d2 = d1.ToDictionary(kvp => kvp.Key, kvp => int.Parse(kvp.Value));

Since Dictionary<TKey, TValue> class implements IEnumerable<KeyValuePair<TKey,TValue>> and ToDictionary is extension method for IEnumerable<T> the code above works fine

Answer 2

Please try this:

var d1 = new Dictionary<string, string>() {
    { "One", "1" },
    { "Two", "2" }
};

// map dictionary 1 to dictionary 2 with LINQ
var d2 = d1.ToDictionary(kvp => kvp.Value, kvp => int.Parse(kvp.Value));