The System.Transaction assembly is not part of the .net core framework at the moment (see https://github.com/dotnet/corefx/issues/2949). In my application (asp.net core mvc)
Just wanted to leave a comment here in case anybody wandered by this post while researching this issue. I ran into this randomly on .net core 2.1 using Dapper, which includes System.Data.SqlClient 4.5.0 by default. Adding version System.Data.SqlClient 4.5.1 independently via nuget worked. So it seems this has been fixed as of 4.5.1.
The following are the relevant sections of my csproj file: