Question

I have a dictionary like

public Dictionary<DateTime, Dictionary<string, string>> dicCollection 

How can I add more values to the same key in this dictionary?

Using C# 3.0

Answer 1

If you’re trying to add values to the outer dictionary in your example, you could use code like this:

if(dicCollection.ContainsKey(someDateTime))
    dicCollection[someDateTime].Add("key","value");
else
{
    Dictionary<string, string> newInner = new Dictionary<string, string>();
    newInner.Add("key","value");
    dicCollection.Add(someDateTime, newInner);
}

That will ensure that when a new key gets added to the outer dictionary, the inner dictionary won’t be null (if it were null, calling Add would throw a null reference exception).