Collection Initializers

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File this in my learn something new every day bucket. I received an email from Steve Maine after he read a blog post in which I discuss the anonymous object as dictionary trick that Eilon came up with.

He mentioned that there is an object initializer syntax for collections and dictionaries.

var foo = new Dictionary<string, string>()
{
  { "key1", "value1" },
  { "key2", "value2" }
};

That’s pretty nice!

Here is a post by Mads Torgersen about collections and collection initializers.

Naturally someone will mention that the Ruby syntax is even cleaner (I know, because I was about to say that).

However, suppose C# introduced such syntax:

var foo = {"key1" => "value1", 2 => 3};

What should be the default type for the key and values? Should this always produce Dictionary<object, object>? Or should it attempt type inference for the best match? Or should there be a funky new syntax for specifying types?

var foo = <string, object> {"key1" => "value1", "2" => 3};

My vote would be for type inference. If the inferred type is not the one you want, then you have to resort to the full declaration.

Then again, the initializer syntax that does exist is much better than the old way of doing it, so I’m happy with it for now. In working with a statically typed language, I don’t expect that all idioms for dynamic languages will translate over in as terse a form.

Check out this use of lambda expressions by Alex Henderson to create a hash that is very similar in style to what ruby hashes look like. Thanks Sergio for pointing that out in the comments.

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