[Everyday C#] Phase E, PR 14a: Statements: collections + LINQ

[BillWagner]

Everyday C# — Phase E, PR 14a: Statements: collections + LINQ

Closes #53556

Adds two example-heavy Fundamentals concept articles under fundamentals/statements/, each backed by a compiling net10.0 snippet project, and wires them into the TOC. Every code sample is included from an external snippet via :::code regions and shows its result as a trailing // => comment; the samples saturate the everyday feature set (collection expressions, file-scoped namespaces, nullable enabled, target-typed new).

New articles

• fundamentals/statements/collections.md — arrays, List<T>, Dictionary<TKey,TValue>; adding, removing, and searching elements; collection expressions (C# 12); indexes and ranges (C# 8) applied to collections. Introduces collection, element, sequence vs map, generic type / type safety, index, range, and collection expression at first use.
• fundamentals/statements/linq.md — query syntax and method (fluent) syntax; the functional trio filter / map / reduce mapped to Where / Select / Aggregate·Sum·Count, plus OrderBy and GroupBy; lambda (anonymous function) expressions in LINQ; deferred execution vs eager evaluation. Names LINQ providers as a first-class use and links out for provider-based queries.

TOC

Collections and LINQ added under Fundamentals → Expressions and statements, after Iteration statements.

Scope discipline — deliberately left out of Fundamentals (link-out targets)

No existing content was cut (both articles are new); the following advanced topics are intentionally kept out of Fundamentals and linked to their proper homes, per Goal 11 / Filter A:

• collections.md → language-reference/builtin-types/arrays.md / collections.md → multidimensional arrays, covariance, collection taxonomy are reference-level.
• collections.md → language-reference/operators/collection-expressions.md / member-access-operators.md → conversion/spread rules and full []/^/.. operator rules are reference-level.
• collections.md → standard/collections/* → choosing among specialized/concurrent/immutable collections and custom comparers fail universality.
• linq.md → linq/* (LINQ section) → joins, providers/IQueryable, deferred-execution mechanics, custom operators, XML/EF behavior are LINQ-focus material.
• linq.md → PLINQ / expression trees / performance → parallel and advanced-representation material.

Validation

• Both snippet projects build clean (0 warnings, 0 errors) on net10.0; every // => output verified by running the programs.
• All relative links, the #indexer-operator- anchor, and all <xref:...> UIDs verified to resolve; version claims (collection expressions → C# 12, ^/.. → C# 8) confirmed.
• No programming-guide/* link destinations (that area is slated for retirement).

Opened as draft for review.

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Internal previews

📄 File	🔗 Preview link
docs/csharp/fundamentals/statements/collections.md	Common collection types
docs/csharp/fundamentals/statements/linq.md	"LINQ queries in C#"
docs/csharp/toc.yml	Taken from https://github.com/dotnet/roslyn/wiki/Samples-and-Walkthroughs

[Copilot]

Pull request overview

Adds two new “Everyday C#” Fundamentals concept articles under fundamentals/statements/ (Collections and LINQ), backed by new compiling snippet projects, and wires both pages into the C# TOC.

Changes:

• Adds new Fundamentals articles: Collections and LINQ queries.
• Adds new snippet projects (collections-statements and linq-statements) that supply all referenced :::code regions.
• Updates docs/csharp/toc.yml to include the new pages under Fundamentals → Expressions and statements.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
docs/csharp/toc.yml	Adds TOC entries for the new Collections and LINQ Fundamentals pages.
docs/csharp/fundamentals/statements/collections.md	New concept article introducing arrays, List<T>, dictionaries, collection expressions, and indexes/ranges with snippet-backed examples.
docs/csharp/fundamentals/statements/linq.md	New concept article introducing LINQ query/method syntax, common operators, grouping, and deferred execution with snippet-backed examples.
docs/csharp/fundamentals/statements/snippets/collections-statements/Program.cs	Snippet source for the Collections article :::code regions.
docs/csharp/fundamentals/statements/snippets/collections-statements/collections-statements.csproj	New net10.0 snippet project for Collections examples.
docs/csharp/fundamentals/statements/snippets/linq-statements/Program.cs	Snippet source for the LINQ article :::code regions.
docs/csharp/fundamentals/statements/snippets/linq-statements/linq-statements.csproj	New net10.0 snippet project for LINQ examples.