Should I always use TryGetValue to access .net Dictionaries?

Question

In another SO question, I've seen several people recommend me to always use TryGetValue.

While I always use TryGetValue over the Contains?/Access pattern, I avoid this pattern on purpose when I expect the key to always be in the dictionary. I then go for a direct indexer access, so that an exception is raised if the key isn't there, because something unexpected really happened (i.e. the key wasn't in the dictionary while I expect it to).

Since there seems to be a general consensus against my "best-practice" (3 out of 4 people on the post I mentioned explicitly advised to use TryGetValue at all time), I'm eager to read an extended discussion on that topic...

Answer 1

No, you're entirely right IMO.

There's no point in doing:

if (dict.TryGetValue(key, out value))
{
    // whatever
}
else
{
    throw new SomeException("key '" + key + "' wasn't in dictionary");
}

The only benefit of that over:

value = dict[key];

is that you get a more explicit exception message... but at the cost of readability, IMO.

It's like casting vs using as - an exception is the right result when the state is "wrong", so use the form which gives that behaviour.