Get 3 parameters out of a Dictionary<string, Dictionary<string Action>>

if (!roomfurnitures.ContainsKey(roomtype))
    roomfurnitures[roomtype] = new Dictionary<string, string>(); // the first time we've seen this

// get the dictionary for the specific room
var room = roomfurnitures[roomtype];

// now we can add the furniture to the room
room[item] = description;

var result = yourMainDict.OrderBy(x => x.Value.Sum(v => v.Value.Delivered + v.Value.Submitted + v.Value.Failed));

var foo = new Dictionary<string, Dictionary<string, List<MyCustomClass>>>();
...
// Add some content to foo.
...

string nameOfMyList = ""; // Something that exists as a key in foo.

Dictionary<string, List<MyCustomClass>> result = foo[nameOfMyList];

var result = differences.SelectMany(y => y).OrderBy(x => x.Key).First();

 matched = myData
    .SelectMany(kv => kv.Value)
    .Where(dict => dict.TryGetValue(givenKey, out string value) && value == givenValue)
    .ToList();