Can I initialize a BCL immutable collection using braces?

Question

In the old days, we could conveniently initialize mutable collections using braces, as in the following example:

var myDictionary = new Dictionary<string, decimal> {{"hello", 0m}, {"world", 1m}};

Is there a similar syntax that can be used with BCL immutable collections? I understand it is still a pre-release but maybe there is a recommended syntax, or at least this question will serve as feedback to implement these convenient initializers.

In the mean time, the shortest I have found is the following:

var myDictionary = new Dictionary<string, decimal> {{"hello", 0m}, {"world", 1m}}.ToImmutableDictionary();

Answer 1

Is there a similar syntax that can be used with BCL immutable collections?

Not as far as I'm aware - unfortunately both object and collection initializers rely on mutability. In that respect it's a shame that the language isn't designed such that if there's an Add method with a return value, that can be used as an intermediate value. (That wouldn't help with setting properties in object initializers, mind you, and I prefer the name Plus to Add to make the semantics clearer.)

I think the approach you're already using is the most appropriate one for a shortcut.

For ImmutableList it's slightly simpler:

var list = ImmutableList.Create(1, 2, 3);

which is fairly simple (and allows for type inference) but I don't know of anything similar for ImmutableDictionary. There's an overload of Create which takes an IEnumerable<TKey, TValue>, but constructing any implementation is likely to be as fiddly as just constructing the mutable dictionary as you're already doing.