What's New in C# 8.0

The Discussion

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  absolute *

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  How to set project level nullable context?

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  Cool thanks! :D

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  What is in store for VB.net?

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  @Jan Willem Zondag: 

  in .csproj file:

  <PropertyGroup>
    ...
    <NullableReferenceTypes>true</NullableReferenceTypes>
    <LangVersion>8.0</LangVersion>
  </PropertyGroup>

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  What is "default" for non-nullable string?
  
  string str = default; // converting null literal or possible null value to non- / // nullable type
  
  This gives the same warning as replacing "default" with null;

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  @ArneG: Kathleen posted about VB a couple of weeks ago:
  https://blogs.msdn.microsoft.com/vbteam/2018/11/12/visual-basic-in-net-core-3-0/

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  @GodwinK: Nullable reference types do not change runtime semantics of the language - all they do is add warnings. So default(string) remains null, but gets a warning.

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  For a kind of project i am doing i am generating a schema from functions header/prototype. Currently i have two generic classes NonNull<T> and Nullable<T>. My version of Nullable is different to C#'s.
  
  void MyFunc(NonNull<string> a, Nullable<string> b)
  {
  
  }
  
  Then i generate some schema using Reflection in run-time.
  
  I tried the same thing with C# 8.0 but running Console.WriteLine(typeof(string?).Name) prints String.
  
  Is there any solution i can know if the function argument is nullable or not ?

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  Can the IAsyncEnumerable already be tested in Visual Studop 2019 prview 1 with .NET Core SDK 3.0.100-preview-009812?

  While consuming seems to be no problem using yield return in an Method returning IAsyncEnumerable can't compile. With an strange error

  C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\MSBuild\15.0\Bin\Roslyn\Microsoft.CSharp.Core.targets(52,5): error MSB6006: "csc.exe" wurde mit dem Code -2146232797 beendet.

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  LokiMidgard, this is what happens when you have German developers in your team :-))))

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  - nullable - one of the best improvements ever
  - asynch streams - good, but maybe not such a common use case
  - switch expressions - hmmm. The example shows that maybe you designed the solution to the problem in the wrong way. having an List<string> names would naturally solve the problem. Or maybe even better List<(int nameType, string name> names. But I have to play around to see if this will help me
  - default interface methods - good, some risk of getting back in the multi-inheritance complexity issues of C++. Have an eye on it before doing more
  - less typing where things are clear - perfect

   

  Overall I really appreciate the carefully executed continious improvements of the C# language, adding those features that really deliver additional value.

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  This is really good. I've been playing with it for a bit now; huge improvements and greatly appreciated.  

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  Glad to see pattern matching make it into the language, it will help a lot.