How to use LINQ to find a sum?

Question

I have this structure:

private readonly Dictionary<string, Dictionary<string, int>> _storage =     new Dictionary<string, Dictionary<string, int>>(); 

key: Firmware(string): key: Device(string) : value CountOfUsers (int)

I need to get the total of users for each device, but I really don't know how to do it with LINQ. Already tried a lot of variants. Please, help!

For now, I just use a whole function for it

private XlsRow2 GetTotalPerDevice(Dictionary<string, Dictionary<string, int>> storage)     {         XlsRow2 totalPerDeviceRow = new XlsRow2();         totalPerDeviceRow._Name = "Grand Total";         totalPerDeviceRow.UseBorders = true;         foreach (var deviceModel in _allDeviceModels)         {             foreach (var firmware in storage)             {                 foreach (var device in firmware.Value)                 {                     var countOfUsers = 0;                     if (deviceModel == device.Key)                     {                         countOfUsers += device.Value;                          if (!_totalsPerDevice.ContainsKey(deviceModel))                         {                             _totalsPerDevice.Add(deviceModel, countOfUsers);                         }                         else                         {                             _totalsPerDevice[deviceModel] += countOfUsers;                         }                     }                 }             }         }         foreach (var deviceModel in _allDeviceModels)         {             if (_totalsPerDevice.ContainsKey(deviceModel))             {                 totalPerDeviceRow._AddColumn(_totalsPerDevice.First(k => k.Key == deviceModel.ToString()).Value.ToString());             }             else             {                 totalPerDeviceRow._AddColumn("");             }         }         return totalPerDeviceRow;     } 

Answer 1

Something like this for example?

var result = _storage.SelectMany(x => x.Value)     .GroupBy(x => x.Key)     .Select(x => new { Device = x.Key, Total = x.Sum(y => y.Value) }); 

Answer 2

Since the keys for the data that you would like to aggregate is in the second-level dictionary, a good first step would be to dump all key-value pairs from inner dictionaries into a flat sequence. After that all you need is to aggregate the counts, like this:

var res = _storage     .SelectMany(d => d.Value)     .GroupBy(kvp => kvp.Key)     .ToDictionary(g => g.Key, g => g.Sum(kvp => kvp.Value));