C# 13 brings several enhancements and new features, focusing on developer productivity, readability, and performance. Here’s an overview of the key additions and improvements in C# 13:

1. Enhanced Pattern Matching

• Improved Relational Patterns: Combine multiple relational patterns using logical operators (and, or, not) for concise expressions.
• List Patterns: Match against lists or arrays with specific conditions, e.g., checking for specific elements or patterns at the start or end of a list.
• Recursive Patterns: Enhanced support for matching nested objects and complex hierarchies.

2. Enhanced String Interpolation

• Interpolation in Interpolated Strings: Easier nesting of interpolated strings inside each other.
• Performance Improvements: Optimized string interpolation for scenarios with frequent usage, making it faster and more memory-efficient.

3. Improved using Directives

• Scoped using Directives: More control over the scope of using statements. This helps reduce clutter and unintended namespace pollution.

4. Default Parameter Support in Lambdas

• Lambdas can now accept default parameters, bringing them closer to regular method behavior:
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  var greet = (string name = "World") => $"Hello, {name}!"; Console.WriteLine(greet()); // Output: Hello, World!

5. File-Scoped Types

• A new syntax to declare types that are scoped to a single file, preventing them from being used elsewhere in the project.

6. typeof Enhancements

• You can now use typeof in more contexts, including generic parameter constraints and default values.

7. Improvements to LINQ

• New LINQ features and optimizations for better performance in querying data sources.
• Additional LINQ methods for more expressive query patterns.

8. Static Abstract Members in Interfaces

• Building on previous features, C# 13 further improves support for static abstract members in interfaces, enabling more powerful generic programming scenarios.

9. Improved Nullable Reference Types

• Enhanced tools and diagnostics for working with nullable reference types to ensure better null-safety in your code.

10. Extended switch Expressions

• More concise and readable switch expressions with additional syntax capabilities, especially when working with patterns.

11. Performance and Compiler Optimizations

• The compiler introduces various optimizations to reduce build time and improve runtime performance for common scenarios.

12. Attributes on Lambda Expressions

• You can now apply attributes to lambda expressions, useful for scenarios like diagnostics or runtime behavior tuning.

Example Highlights:

C# 13 continues to make coding more expressive, concise, and performant. For more details, you can refer to Microsoft’s official documentation or the C# Language Design Notes.

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