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Hello,
I want to use the new feature in C#12, but the compiler doesn't know this feature.
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Hi @Shervan360 , Welcome to Microsoft Q&A,
You need to read the version that applies to C# 12.
C# 12 includes the following new features. You can try these features using the latest Visual Studio 2022 version or the .NET 8 SDK.
Alias any type
You can use the using alias directive to alias any type, not just named types. That means you can create semantic aliases for tuple types, array types, pointer types, or other unsafe types. For more information, see the feature specification. For an example refactoring walkthrough, see Refactor your code using alias any type on the .NET blog.
// This is not legal.
// Error CS9132: Using alias cannot be a nullable reference type
using X = string?;
// This is legal.
// The alias is to `List<...>` which is itself not a nullable
// reference type itself, even though it contains one as a type argument.
using Y = System.Collections.Generic.List<string?>;
// This is legal.
// This is a nullable *value* type, not a nullable *reference* type.
using Z = int?;
Best Regards,
Jiale
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Thank you, I have the latest of .NET, VS 2022, and C# 12.
Is there any update in this issue?
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Your issue is that type alias definitions are not allowed in code blocks. Move the definition to before the class definition.