What is the difference between 'dependencies' and 'frameworkAssemblies' in project.json?

Question

The documentation for using project.json for ASP.NET 5 applications includes a sample project.json file (abbreviated version below).

What is the difference between frameworkAssemblies and dependencies?

And why does dnx451 use one and dnxcore50 use the other?

{
  "version": "0.1-alpha-*",
  ...
  "frameworks": {
    "dnx451": {
     "frameworkAssemblies": {
        ...
      }
    },
    "dnxcore50": {
     "dependencies": {
       ...
     }
  }
}

Answer 1

frameworkAssemblies refers to assemblies present in GAC (global assembly cache).

Consider the following example:
I want to use ADO.NET apis(SqlConnection, SqlCommand) to work with a SQL Server database. I know that these apis are part of System.Data.dll and so want to reference it. Now when the full version of .NET Framework is installed, it installs some assemblies in the GAC (which has this System.Data.dll too) and hence you see a reference to frameworkassemblies in the below example. Coming to CoreClr, I need to find out in which package these types exist. For this you could use the website called PackageSearch(built by an ASP.NET team member) where you can search for a type and find the package name. Based on this you will find System.Data.SqlClient to be the package. Since this package is built for CoreClr, it is part of dependencies section within the dnxcore50 section.

{
    "version": "1.0.0-*",
    "description": "Test App",
    "dependencies": {
    },
    "frameworks": {
        "dnx451": {
            "frameworkAssemblies": {
                "System.Data": "4.0.0.0"
            }
        },
        "dnxcore50": {
            "dependencies": {
                "System.Data.SqlClient": "4.0.0-beta-*"
            }
        }
    }
}

Now let's say you want to even add support for json serialization and deserialization in your app and want to reference Json.Net nuget package. Json.Net nuget package supports both the desktop and core clr and hence you would put it in the dependencies section common to both frameworks.

{
    "version": "1.0.0-*",
    "description": "Test App",
    "dependencies": {
        "Newtonsoft.Json": "6.0.6"
    },
    "frameworks": {
        "dnx451": {
            "frameworkAssemblies": {
                "System.Data": "4.0.0.0"
            }
        },
        "dnxcore50": {
            "dependencies": {
                "System.Data.SqlClient": "4.0.0-beta-*"
            }
        }
    }
}