Add new constructor to AvaloniaDictionary and include unit tests #17311

[IoannTerrible]

#17311

What does the pull request do?

This pull request adds a new constructor to AvaloniaDictionary<TKey, TValue> that accepts an existing Dictionary<TKey, TValue>. The goal is to provide an easier and more efficient way to initialize AvaloniaDictionary with pre-existing dictionary data.

What is the current behavior?

Currently, AvaloniaDictionary lacks a constructor that directly accepts a Dictionary<TKey, TValue>. Developers have to manually copy elements into AvaloniaDictionary, which increases boilerplate code and is less efficient.

What is the updated/expected behavior with this PR?

With this PR, developers can initialize AvaloniaDictionary with an existing dictionary directly, simplifying the code and reducing manual effort.
To test:

• You can create an AvaloniaDictionary by passing a populated dictionary and verify that all entries are correctly initialized.
• Passing null should throw an ArgumentNullException.

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

No breaking changes are introduced, as this PR simply adds an overload to the existing constructors.

Obsoletions / Deprecations

Fixed issues

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0052726-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[cla-avalonia]

• All contributors have signed the CLA.

[IoannTerrible]

@cla-avalonia agree

[robloo]

Should the new constructor be an IDictionary interface rather than concrete class?

[maxkatz6]

This ctor overload seems to be the most complete:
https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2.-ctor?view=net-8.0#system-collections-generic-dictionary-2-ctor(system-collections-generic-ienumerable((system-collections-generic-keyvaluepair((-0-1))))-system-collections-generic-iequalitycomparer((-0)))

[MrJul]

API diff for review:

namespace Avalonia.Collections
{
     public partial class AvaloniaDictionary {
     {
+        public AvaloniaDictionary(System.Collections.Generic.Dictionary<TKey, TValue> initialDictionary) { }
     }
}

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0054275-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[MrJul]

Notes from the API meeting:

As suggested in #17312 (comment), use the most complete constructor.

Expected API:
AvaloniaDictionary(IEnumerable<KeyValuePair<TKey,TValue>> collection, IEqualityComparer<TKey>? comparer);

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0054395-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[MrJul]

LGTM, thank you!

[MrJul]

Nit: you can remove this check and the throw below. Let the Dictionary's constructor throw on its own, as its documented to do so. There's no real point in checking the same thing several times.