Merging Dictonaries in C# using LINQ

Question

i\'ve three Dictonaries like

Dictionary> D1 = new Dictionary>(); 
Dictionary

        

Answer 1

Something like this (maybe needs optimisation)?

     var lr =
    (from gr in
        (from pair in D1.Union(D2).Union(D3)
         group pair by pair.Key)
     select new KeyValuePair>>(gr.Key, gr.Select(x => x.Value))
    ).ToDictionary(k => k.Key, v => v.Value.Aggregate((t, s) => (new List(t.Union(s)))));