Adapt project for vs2017(using vs2019 leads to an error 'Could not load type of field')

build/common.targets

@@ -11,6 +11,12 @@
     <DefineConstants Condition="$(OS) == 'Windows_NT'">$(DefineConstants);SMAPI_FOR_WINDOWS</DefineConstants>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Net.Compilers" Version="3.3.1">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
   <!-- if game path is invalid, show one user-friendly error instead of a slew of reference errors -->
   <Target Name="ValidateInstallPath" AfterTargets="BeforeBuild">
     <Error Condition="!Exists('$(GamePath)')" Text="Failed to find the game install path automatically. You can specify where to find it; see https://smapi.io/package/custom-game-path." />

src/SMAPI/Framework/Networking/SGalaxyNetClient.cs

@@ -1,4 +1,3 @@
-#if SMAPI_FOR_WINDOWS
 using System;
 using Galaxy.Api;
 using StardewValley.Network;
@@ -50,4 +49,3 @@ namespace StardewModdingAPI.Framework.Networking
         }
     }
 }
-#endif

src/SMAPI/Framework/Networking/SGalaxyNetServer.cs

@@ -1,4 +1,3 @@
-#if SMAPI_FOR_WINDOWS
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
@@ -74,4 +73,3 @@ namespace StardewModdingAPI.Framework.Networking
         }
     }
 }
-#endif

src/SMAPI/Framework/Networking/SLidgrenClient.cs

@@ -1,4 +1,3 @@
-#if SMAPI_FOR_WINDOWS
 using System;
 using StardewValley.Network;
 
@@ -49,4 +48,3 @@ namespace StardewModdingAPI.Framework.Networking
         }
     }
 }
-#endif

src/SMAPI/Framework/Networking/SLidgrenServer.cs

@@ -1,4 +1,3 @@
-#if SMAPI_FOR_WINDOWS
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
@@ -68,4 +67,3 @@ namespace StardewModdingAPI.Framework.Networking
         }
     }
 }
-#endif

src/SMAPI/SMAPI.csproj

@@ -26,6 +26,7 @@
     <DefineConstants>DEBUG;TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <LangVersion>latest</LangVersion>
     <LangVersion>8.0</LangVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">