Half-Blood Programmer

Porting #SNMP Library to .NET Core Once Again

You probably know that I have ported this library to .NET Core a few months ago,

Overall things work as Microsoft promised, but the process was rather painful. So instead of quickly moving everything to .NET Core, I decided to stay on .NET Framework and move a few goodies from the .NET Core migration attempt back to 9.0.x series.

It turns out to be a smart choice as Microsoft later shipped Visual Studio 2017 RC (refreshed a few days ago), and today I can use an IDE to migrate once again. But I do hit a few different issues, so I’d like to list below.

MSBuild Project

First I created an empty .NET standard 1.3 class library project, and then put it into SharpSnmpLib folder. The new format of MSBuild scripts allow the project to automatically include all C# source files without my manually adding them all. But immediately I hit an error that many existing attributes are duplicate such as,

error CS0579: Duplicate ‘System.Reflection.AssemblyCompanyAttribute’ attribute.

I was able to find similar posts on Stack Overflow and GitHub, but my solution is to add conditionals in AssemblyInfo.cs to exclude certain attributes from .NET Core compilation.

Missing Packages

The remaining errors are so common that still classes or methods are missing. And I have to manually edit .csproj to add necessary packages in Visual Studio Code, where I can run “dotnet restore” and “dotnet build” at integrated terminal to observe errors,

<ItemGroup>

<PackageReference Include=”NETStandard.Library” Version=”1.6″ />

<PackageReference Include=”System.AppDomain” Version=”2.0.11″ />

<PackageReference Include=”System.ComponentModel.TypeConverter” Version=”4.1.0″ />

<PackageReference Include=”System.Net.NetworkInformation” Version=”4.1″ />

<PackageReference Include=”System.Runtime” Version=”4.1″ />

<PackageReference Include=”System.Runtime.Serialization.Primitives” Version=”4.1.1″ />

<PackageReference Include=”System.Threading.Thread” Version=”4.0.0″ />

</ItemGroup>

You might notice a quite strange package “System.AppDomain”, which comes from a third party, https://www.nuget.org/packages/System.AppDomain/. So Microsoft does have AppDomain support in CoreCLR but intentionally hides that in CoreFX. This package exposes some important API, but not all.

Conditionals

Still I have to leave conditional compilation from time to time, but compared to the previous attempts, the number has decreased, which is quite a pleasure. I no longer need to remove the sync versions of the Socket related methods, as the underlying API is back in .NET standard 1.3.

You can check the whole commit here,

https://github.com/lextm/sharpsnmplib/commit/a26d8af07f04d095c903d61ee923ce66286dd316

Sidenote

I also hit one Visual Studio 2017 limitation where after compiling the .NET standard solution, the classic solution cannot be compiled properly,

https://developercommunity.visualstudio.com/content/problem/9051/microsoftnugettargets-error-when-compiling-a-pcl-p.html

Luckily a workaround was found and documented in the link above.

Hope you enjoy Visual Studio 2017 RC as I do. .NET Core is becoming mature, and the prime time is coming. Stay tuned.

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