Group dictionary to other dictionary via intermediate map-CodePudding

I have a dictionary that map between certain keys

var map = new Dictionary<string, string>(){ {"A", "One"}, {"B", "One"}, {"C", "Two"} };

I also have a dictionary containing values

var values = new Dictionary<string, double>() { {"A", 2.0}, {"B", 1.0}, {"C", 1.0} };

I want to map the values into a third dictionary so that the value of map is the key of the new dictionary. I.e. I want the new dictionary to be

var result = new Dictionary<string, double>() {{"One", 3.0}, {"Two", 1.0}};

This can of course be achieved using loops like so

var result = new Dictionary<string, double>();
foreach (var kv in values)
{
    var key = map[kv.Key];
    var value = kv.Value;

    if (result.TryGetValue(key, out var temp))
        result[key] = value   temp;
    else
        result.Add(key, value);
}

Or something like that...

But is it possible to do this in a one-liner using linq?

CodePudding user response：

Try this,

var result = map
 .Join(values, x => x.Key, y => y.Key, (x, y) => (x.Value, y.Value))
 .GroupBy(x => x.Item1)
 .ToDictionary(x => x.Key, y => y.Sum(s => s.Item2));

DotNet Fiddle: https://dotnetfiddle.net/tWd9j5

CodePudding user response：

Looks like you're looking for Join method

var result = map.Join(values, x => x.Key, y => y.Key, (x, y) => (x.Value, y.Value)).ToDictionary(x => x.Item1, y => y.Item2);

And to handle duplication of value

var result = map
            .Join(values, x => x.Key, y => y.Key, (x, y) => (x.Value, y.Value))
            .GroupBy(x => x.Item1)
            .ToDictionary(x => x.Key, y => y.First().Item2);

CodePudding user response：

Sure you can.

var result = (from m in map
                      join v in values
                      on m.Key equals v.Key
                      group v.Value by m.Value into sameVal
                      select new { MValue = sameVal.Key, VValue = sameVal.Sum() }).ToDictionary(a => a.MValue, b => b.VValue);