using System;

using System.Linq;

using System.Xml;                   

using System.Xml.Linq;

using System.Collections; 

using System.Collections.Generic;

using System.Data;

using System.Data.DataSetExtensions;

using System.Data.Linq;

using System.Text;

using System.Text.RegularExpressions;

using System.Xml.Serialization; 

using System.IO;

using System.Globalization;

using System.Diagnostics;

​

public class Program

{

    public static void Main()

    {

        Dictionary<char, int> dic1 = new Dictionary<char,int>()

        {

            {'a', 2},               

            {'b', 2},

            {'c', 2},

            {'d', 2},   

        };

        Dictionary<char, int> dic2 = new Dictionary<char,int>()

        {

            {'a', 1},               

            {'b', 2},

            {'c', 4},

            {'e', 2},   

        };

        dic1.Concat(dic2)

            .GroupBy(g=>g.Key)

            .ToDictionary(x=>x.Key, x=>x.Max(m=>m.Value))

            .Dump();

    }

}