AsMutable extension method

[emphasis87]

Would it be possible to have a shorthand extension method to convert IReadOnly types (set, dictionary, list) back to mutable ones?

[huoyaoyuan]

No, because same data types are designed without mutable support in order to minimize copying, especially the Immutable* ones.

[huoyaoyuan]

readOnlyDictionary?.AsMutable() ?? new Dictionary<string, string>()

Such code is really confusing. You get a mutable collection with the same content of your given readonly collection, but whether the changes is observable with the original readonly collection reference is not determined.

If you have the requirement to use readonly collections and have mutated versions of them, does ImmutableDictionary or FrozenDictionary meet your requirement?

[huoyaoyuan]

It seemed to me that AsMutable could be a nice counterpart to AsReadOnly extension method, which are clear in allocating a new object.

AsReadOnly has a clear contract that the input and output reference will view the same content and changes. Such constraint can't be satisfied for AsMutable.

[emphasis87]

Ah, I see. I mistakenly thought that AsReadOnly<TKey,TValue>(IDictionary<TKey,TValue>) returns a new collection, but it is only a wrapper. My use case is that I have a public dictionary that should not be edited once populated, and then I need to create another dictionary starting with the same values, then extending it and then again setting it to a public property as not editable.

[emphasis87]

At first I tried to solve it by Enumerable.ToDictionary, but that involved unnecessary lambdas. So, anyway, I think I will mark it as answered, for now. Unless ReadOnlyDictionary.ToDictionary extension method becomes a possibility?

[huoyaoyuan]

At first I tried to solve it by Enumerable.ToDictionary, but that involved unnecessary lambdas.

See #65925.