Update CA1873 to recommend source-generated logging with LoggerMessageAttribute

[Copilot]

CA1873 documentation recommended the older LoggerMessage pattern. Updated to recommend source-generated logging with LoggerMessageAttribute (available since .NET 6).

Changes

• Rule description and fix guidance: Changed from LoggerMessage pattern to LoggerMessageAttribute on partial methods
• Code examples: Replaced inline code with compilable C# and VB snippets demonstrating:
  • Violations: expensive operations in logging arguments (string.Join, object creation)
  • Fixes: source-generated logging that defers evaluation until log level check

Before

// Fix: Guard with IsEnabled check
if (_logger.IsEnabled(LogLevel.Debug))
{
    _logger.LogDebug($"Processing {string.Join(", ", data)} items");
}

After

// Fix: Source-generated logging
public void ProcessData(int[] data)
{
    LogProcessingData(data);  // No expensive operation unless enabled
}

[LoggerMessage(Level = LogLevel.Debug, Message = "Processing {Data} items")]
private partial void LogProcessingData(int[] data);

Aligns with CA1848 and current .NET performance logging best practices.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>CA1873 - Update logging recommendation to source generation</issue_title>
<issue_description>### Type of issue

Typo

Description

Change the recommendation and example for fixing this diagnostic from LoggerMessage to source-generated loggers.

Page URL

https://learn.microsoft.com/en-gb/dotnet/fundamentals/code-analysis/quality-rules/ca1873

Content source URL

https://github.com/dotnet/docs/blob/main/docs/fundamentals/code-analysis/quality-rules/ca1873.md

Document Version Independent Id

b592168a-cc0e-fe99-986e-c1a082228d92

Platform Id

8571c673-bf84-6950-9767-677e8a98e0d3

Article author

@gewarren

Metadata

• ID: d46812eb-4194-0d2b-cce6-a3a658e5fd4d
• PlatformId: 8571c673-bf84-6950-9767-677e8a98e0d3
• Service: dotnet-fundamentals

Related Issues</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes CA1873 - Update logging recommendation to source generation #50135

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Internal previews

📄 File	🔗 Preview link
docs/fundamentals/code-analysis/quality-rules/ca1873.md	CA1873: Avoid potentially expensive logging

[Copilot]

Pull request overview

This PR updates the CA1873 rule documentation to recommend modern source-generated logging with LoggerMessageAttribute instead of the older LoggerMessage pattern. The change aligns CA1873 with CA1848 and current .NET performance logging best practices introduced in .NET 6.

Key Changes

• Updated rule description and fix guidance to recommend source-generated logging with LoggerMessageAttribute on partial methods
• Replaced inline code examples with compilable C# and VB snippet files demonstrating violations (expensive operations like string.Join and object creation in logging arguments) and their fixes using source-generated logging
• Added proper project files targeting .NET 10 with Microsoft.Extensions.Logging package references

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/fundamentals/code-analysis/quality-rules/ca1873.md	Updated rule description, fix guidance, and replaced inline code with snippet references; maintains proper AI-usage frontmatter and documentation structure
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/csharp/CA1873Example/Violation.cs	C# example demonstrating violations: expensive string.Join operation and anonymous object creation in logging arguments
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/csharp/CA1873Example/Fix.cs	C# example showing proper fix using source-generated logging with LoggerMessageAttribute on partial methods
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/csharp/CA1873Example/CA1873Example.csproj	Project file for C# examples targeting net10.0 with Microsoft.Extensions.Logging reference
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/csharp/CA1873Example/Program.cs	Minimal program entry point for C# example project
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/vb/CA1873Example/Violation.vb	VB equivalent of C# violation examples showing same anti-patterns
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/vb/CA1873Example/Fix.vb	VB equivalent of C# fix examples using source-generated logging
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/vb/CA1873Example/CA1873Example.vbproj	Project file for VB examples targeting net10.0 with Microsoft.Extensions.Logging reference
docs/fundamentals/code-analysis/quality-rules/snippets/ca1873/vb/CA1873Example/Program.vb	Minimal program entry point for VB example project

[BillWagner]

This LGTM @gewarren

Let's