如何在 Visual Studio 2017 中使用 C# 8? [英] How can I use C# 8 with Visual Studio 2017?

问题描述

我想在 Visual Studio 2017 中使用 C# 8.0(尤其是范围和不可为空的引用类型).可以吗?

解决方案

展望未来，微软希望将 C# 语言版本与过去的框架版本更紧密地联系在一起.他们真的只希望您将 C# 8 与 .NET Core 3.x 和 .NET Standard 2.1 项目一起使用，这意味着使用 Visual Studio 2019.我对

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如果您想尝试一下，这里是 .csproj 和代码:

<Project Sdk="Microsoft.NET.Sdk"><属性组><TargetFrameworks>netstandard2.0;net452</TargetFrameworks><LangVersion>8.0</LangVersion><Nullable>启用</Nullable></属性组><项目组><PackageReference Include="Microsoft.Net.Compilers" 版本="3.3.1"><PrivateAssets>所有</PrivateAssets><IncludeAssets>运行时；建造;本国的;内容文件；分析器</IncludeAssets></包参考></项目组></项目>

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使用系统；命名空间 CSharp8Test{公共课 Class1{公共字符串?NullableString { 得到；} = "测试";公共静态无效测试(){Console.WriteLine(Test2());静态 int Test2() =>5个；}}}

I'd like to use C# 8.0 (especially ranges and non-nullable reference types) in Visual Studio 2017. Is it possible?

解决方案

Going forward, Microsoft want to tie C# language versions more closely to framework versions than they have in the past. They really only want you to be using C# 8 with .NET Core 3.x and .NET Standard 2.1 projects, and that means using Visual Studio 2019. My answer to Does C# 8 support the .NET Framework? has all the gory details.

However, if you really want to you can now use C# 8 in Visual Studio 2017 by using the same trick that brings C# 7 to Visual Studio 2015: install the latest version of the Microsoft.Net.Compilers Nuget package into the project. It works, but of course VS 2017 doesn't know about C# 8 syntax so it doesn't look very pretty. Here's a screenshot showing that VS 2017 is able to compile a small test library using nullable reference types and a static local method (both of which are C# 8 features):

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Here's the .csproj and code if you want to try it:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFrameworks>netstandard2.0;net452</TargetFrameworks>
    <LangVersion>8.0</LangVersion>    
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Net.Compilers" Version="3.3.1">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
    </PackageReference>
  </ItemGroup>
</Project>

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using System;

namespace CSharp8Test
{
    public class Class1
    {
        public string? NullableString { get; } = "Test";

        public static void Test()
        {
            Console.WriteLine(Test2());
            static int Test2() => 5;
        }
    }
}

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