cannot convert from Dictionary to IDictionary

Question

I'm trying to create interface with method

void Import(int id, IDictionary<int, IDictionary<int, string>> items);

then call this method like

Dictionary<int, Dictionary<int, string>> items = viewModel.Items
  .GroupBy(t => t.Number)
  .ToDictionary(t => t.Key, t => t.ToDictionary(x => x.LanguageId, x => x.Translation));


Import(id, items);

I expected that it should works but got an error

cannot convert from 'System.Collections.Generic.Dictionary<int, System.Collections.Generic.Dictionary<int, string>>' to 'System.Collections.Generic.IDictionary<int, System.Collections.Generic.IDictionary<int, string>>'  

Why I can't use interface IDictionary here? Should I cast manually?

Answer 1

Change your assigning type.

Dictionary<int, IDictionary<int, string>> items = viewModel.Items
  .GroupBy(t => t.Number)
  .ToDictionary(t => t.Key, t => (IDictionary<int, string>) t.ToDictionary(x => x.LanguageId, x => x.Translation));