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C# 9: Minor Improvements for Lambdas
Lambdas will be getting a small upgrade in C# 9 with two new features: discard parameters and static anonymous functions. Neither will change the way code is written, but they do clarify the developer’s intent.
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C# 9: Range Operators in Switch Constructs and Pattern-Matching Expressions
Since C# was first introduced, developers have complained about the lack of a range operator in switch constructs. This made switches far less useful in C# than they were in VB. As part of the pattern-matching enhancements for C# 9, this limitation has been addressed.
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C# 9: New `and`, `or`, and `not` Keywords for Pattern Matching
Though it may sound like our occasional April Fools Day joke, C# 9 is looking to add `and`, `or`, and `not` to its list of keywords. Specifically, for use in pattern matching.
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C# Futures: Null Check Operator
In the June 24th C# Language Design Meeting, Microsoft made a subtle change to the parameter null checking syntax. By changing it from “Type parameterName!” to “Type parameterName!!” they effectively introduced a new ‘null check operator’.
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C# 9: Type Inference for the New Keyword
In many situations, there is only one possible type allowed in a given place. And yet C# still requires you to explicitly list the type. Now that the Target-typed `new` expression proposal has been adopted into C# 9, such boilerplate code will no longer be necessary.
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C# 9: Simplified Parameter Null Validation
Simplified parameter null validation has been promoted to a C# 9 feature. This narrowly tailored feature reduces the amount of code needed to validate non-null parameters to a single character in the function signature.
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C# 9: Partial Method Enhancements for Source Generators
Source Generators in C# 9 will allow compiler-extensions to inspect code and then inject additional source code at compile-time. This injected code is then incorporated into the very same assembly that was being compiled. In order to facilitate this capability, Microsoft is removing most of the restrictions on Partial Methods.
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C# 9: towards First Class Support for Scripting
One of the defining characteristics of “scripting” languages is they don’t need any boilerplate. The very first line of a file can be the declarations and statements you would normally see inside a function. In the updated Top-level statements proposal, this capability is planned for C# 9.
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Fabulous Enables Building Declarative Cross-Platforms UIs for iOS and Android in F#
In a recent Channel 9 show, F# designer and architect Don Syme and Fabulous maintainer Timothé Larivière introduced Fabulous, a community-driven F# framework aimed to build cross-platform mobile and desktop apps based on Xamarin.Forms.
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Source Generators Will Enable Compile-Time Metaprogramming in C# 9
Source generators are a new feature of the C# compiler that enables inspecting user code using compiler-generated metadata and generating additional source files to be compiled along with the rest of the program.
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C# Static Analysis Tool Roslynator.Analyzers Now Has over 500 Ways to Improve Code
The new version 2.3.1 of the Roslynator.Analyzers package brings the number of analyzers, refactorings and fixes to over 500. Roslynator uses the open-source Roslyn .NET Compiler Platform to perform static analysis on your C# code. This analysis drives your IDE to display hints and actions to improve your code.
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C# Futures: Primary Constructors
We last mentioned primary constructors in 2014 when it was removed from the candidate list for C# 6 and VB 12. Late last year, Primary Constructors reappeared as a candidate for C# 9.
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C# Futures: Covariant Return Types
A frequent API design problem is the inability to use a more specific return type when overriding a method. Proposal 49, which is now a C# 9 candidate, seeks to correct this issue.
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C# Futures: Simplified Parameter Null Validation
At first glance, proposal #2145 seems like a logical extension to C# 8’s Nullable Reference Types feature. The basic idea is developers would no longer need to explicitly add argument null checks to methods that accept non-nullable parameters. However, this has become quite contentious.
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C# 9 Proposals: Module Initializers
The module initializer proposal has been promoted to C# 9 candidacy. This would act like a static constructor in C#, but rather than applying to one class it applies to the entire assembly.