dotnet core : Can not find assembly file Microsoft.CSharp.dll

I had <DependsOnNETStandard>true</DependsOnNETStandard> and I had to change it to <DependsOnNETStandard>netstandard1.6</DependsOnNETStandard>

<PropertyGroup>
    <TargetFramework>net462</TargetFramework>
    <RuntimeIdentifier>win7-x64</RuntimeIdentifier>
    <IsServiceFabricServiceProject>True</IsServiceFabricServiceProject>
    <AssemblyName>MyProject</AssemblyName>
    <Platforms>AnyCPU;x64</Platforms>
    <DependsOnNETStandard>netstandard1.6</DependsOnNETStandard>
</PropertyGroup>

Source: From neman on GitHub Isue

In my C# project, a few .NET Standard classlib's support a Core console application and a Winforms .net 4.7 program. Yesterday I opened my project, one of the .NET standard dll's gave above error, leaving references with an exclamation mark, same for all libs that depend on it in the solution ! It looked very alarming.

I kept working on my solution, though.. I use Visual Studio 15.8.1 here, the issue seems to be a spook. A fake warning. The exclamation marks remain while working on the project, but nothing happens, it does not disturb anything or interrupt rebuilds. The assembly runs as expected.

Few minutes ago I solved it, by removing the Microsoft.CSharp reference, then rebuild all. It was in only one library, so the rebuild solved all exclamation marks in the solution. The reference has gone away, clear sky.

I had similar issue where in a .net standard was using "dynamic" type which is there in "Microsoft.CSharp". The project was building from Visual studio but was failing from azure devops release pipeline. adding reference from nuget solved the problem.

Install via https://www.nuget.org/packages/Microsoft.CSharp/ Reference (Credits): https://mikaelkoskinen.net/post/net-core-standard-missing-compiler-required-member