Question

I have this structure:

static Dictionary<int, Dictionary<int, string>> tasks = 
    new Dictionary<int, Dictionary<int, string>>();

it looks like that

[1]([8] => "str1")
[3]([8] => "str2")
[2]([6] => "str3")
[5]([6] => "str4")

I want to get from this list all of the [8] strings, meaning str1 + str2
The method should look like the following:

static List<string> getTasksByNum(int num){

}

How do I access it?

Answer 1

Just iterate over all values of the first hierarchy level and use TryGetValue on the second level:

var result = new List<string>();
foreach(var inner in tasks.Values)
{
    string tmp;
    if(inner.TryGetValue(yourKey, out tmp)
        result.Add(tmp);
}

This solution has a major advantage over all other solutions presented so far:
It actually uses the dictionaries of the second hierarchy level as a dictionary, i.e. the part inside the foreach loop is O(1) instead of O(n) as with all other solutions.