[dotnet] Add nullable reference annotations to Platform

[RenderMichael]

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Description

Adds Nullable Reference Type annotations to the Platform type, as well as modernizes the code surrounding the platform handling.
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Motivation and Context

Contributes to #14640

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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PR Type

enhancement

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Description

• Added nullable reference type annotations to the Platform class, improving code safety and clarity.
• Refactored the Platform class to use auto-properties and modern C# features like switch expressions.
• Simplified platform detection logic in ChromiumDriverService and FirefoxDriverService by using the PlatformID enum instead of integer constants.
• Improved the FromString method in the Platform class to use Enum.TryParse, enhancing robustness.

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Changes walkthrough 📝

Relevant files

Enhancement

ChromiumDriverService.cs Simplify platform detection using PlatformID enum                dotnet/src/webdriver/Chromium/ChromiumDriverService.cs Replaced integer constant with PlatformID enum for Mono Unix. Simplified platform detection logic. +3/-6      FirefoxDriverService.cs Simplify platform detection using PlatformID enum                dotnet/src/webdriver/Firefox/FirefoxDriverService.cs Replaced integer constant with PlatformID enum for Mono Unix. Simplified platform detection logic. +2/-6      Platform.cs Add nullable annotations and modernize Platform class        dotnet/src/webdriver/Platform.cs Enabled nullable reference types. Refactored Platform class to use auto-properties. Simplified IsPlatformType method using switch expressions. Improved FromString method with Enum.TryParse. +34/-81

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PR Reviewer Guide 🔍

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⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Null Reference The current field is marked as nullable but there's no null check in the CurrentPlatform property before dereferencing. While the null-coalescing operator is used, it's good practice to validate this critical platform-dependent code. Platform Detection The platform detection logic in the private constructor doesn't handle all possible PlatformID values. Some modern Windows versions might not be properly detected with the current version checks. Error Handling The FromString method silently falls back to PlatformType.Any when parsing fails. Consider logging a warning or throwing an exception for invalid platform names in debug builds.

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Add support for Mono Unix platform detection to ensure consistent platform handling The platform detection in the constructor should handle the Mono Unix platform (PlatformID 128) to maintain consistency with other parts of the codebase. dotnet/src/webdriver/Platform.cs [105-131] +const PlatformID PlatformIDMonoUnix = (PlatformID)128; switch (Environment.OSVersion.Platform) { case PlatformID.Win32NT: if (this.MajorVersion == 5) { this.PlatformType = PlatformType.XP; } else if (this.MajorVersion == 6) { this.PlatformType = PlatformType.Vista; } else { this.PlatformType = PlatformType.Windows; } break; case PlatformID.MacOSX: this.PlatformType = PlatformType.Mac; break; case PlatformID.Unix: + case PlatformIDMonoUnix: this.PlatformType = PlatformType.Unix; break; } Apply this suggestion Suggestion importance[1-10]: 8 Why: The suggestion ensures consistent platform detection by adding support for Mono Unix (PlatformID 128), aligning with the changes made in other files and preventing potential platform detection issues.	8
	Explicitly handle all platform types in switch expression to prevent potential bugs The switch expression in IsPlatformType method should handle all possible PlatformType enum values explicitly. Add cases for Mac and Unix to avoid potential bugs when new platform types are added. dotnet/src/webdriver/Platform.cs [166-174] return compareTo switch { PlatformType.Any => true, PlatformType.Windows => this.PlatformType is PlatformType.Windows or PlatformType.XP or PlatformType.Vista, PlatformType.Vista => this.PlatformType is PlatformType.Windows or PlatformType.Vista, PlatformType.XP => this.PlatformType is PlatformType.Windows or PlatformType.XP, PlatformType.Linux => this.PlatformType is PlatformType.Linux or PlatformType.Unix, + PlatformType.Mac => this.PlatformType == PlatformType.Mac, + PlatformType.Unix => this.PlatformType == PlatformType.Unix, _ => this.PlatformType == compareTo, }; Apply this suggestion Suggestion importance[1-10]: 7 Why: The suggestion improves code maintainability and robustness by explicitly handling Mac and Unix cases in the switch expression, reducing the risk of bugs when new platform types are added.	7

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[RenderMichael]

The only change I made here was using the modern ??= syntax. If we want to replace this with Lazy<Platform> I can make that change.