Create Solution Folder
c:\Projects>mkdir SampleDotNet
c:\Projects>cd SampleDotNet
Create SampleDotNet solution
c:\Projects\SampleDotNet>dotnet new sln
Create src folder (optional)
c:\Projects\SampleDotNet>mkdir src
c:\Projects\SampleDotNet>cd src
Create Web API Project
c:\Projects\SampleDotNet\src>dotnet new webapi -n SampleDotNet.Api
Create Class Library Project
c:\Projects\SampleDotNet\src>dotnet new classlib -n SampleDotNet.Services
Reference Library Project to Web API Project
c:\Projects\SampleDotNet\src>dotnet add SampleDotNet.Api/SampleDotNet.Api.csproj reference SampleDotNet.Services/SampleDotNet.Services.csproj
Finally Add Projects to Solution
c:\Projects\SampleDotNet\src>cd ..
c:\Projects\SampleDotNet>dotnet sln add src/SampleDotNet.Api/SampleDotNet.Api.csproj
c:\Projects\SampleDotNet>dotnet sln add src/SampleDotNet.Services/SampleDotNet.Services.csproj
Commands

Result
Visual Studio Code

Visual Studio
