gistfile1.cs

public class Program
{
    public void Main()
    {
        var solution = new Directory
        {
            ["global.json"] = new JObject
            {
                ["projects"] = new JArray { "src", "test" }
            },
            ["src"] = new Directory
            {
                ["MyProject"] = new Directory
                {
                    ["Startup.cs"] = "public class Startup { }",
                    ["project.json"] = new JObject
                    {
                        ["dependencies"] = new JObject
                        {
                            ["Newtonsoft.Json"] = "6.0.6"
                        },
                        ["frameworks"] = new JObject
                        {
                            ["dnx451"] = new JObject { }
                        }
                    }
                }
            }
        };
    }
}

project_dsl.fs

type Solution = 
  | SolutionItems of SolutionItem seq
and SolutionItem = 
  | GlobalSettings of GlobalSettings
  | Projects of (string * Project) seq
and GlobalSettings = 
  | ProjectNames of string seq
and Project =
  | ProjectDirectories of (string * ProjectDirectory) seq
and ProjectDirectory = 
  | ProjectItems of (string * ProjectItem) seq
and ProjectItem = 
  | ProjectSettings of (string * ProjectSettingItem) seq
  | SourceFile of string
and ProjectSettingItem = 
  | ProjectDependencies of (string * (ProjectDependency option)) seq
  | ProjectFrameworks of (string * (ProjectFramework option)) seq
and ProjectDependency = 
  | DependencyVersion of string
and ProjectFramework = 
  | FrameworkVersion of string

let solution = 
  SolutionItems [
    GlobalSettings (ProjectNames ["src"; "test"])
    Projects [
      ("src", ProjectDirectories [
        ("MyProject", ProjectItems [ 
          ("Startup.cs", SourceFile ("public class Startup { }"))
          ("project.json", ProjectSettings [
            ("dependencies", ProjectDependencies [ 
              ("Newtonsoft.Json", Some (DependencyVersion "6.0.6"))
            ])
            ("frameworks", ProjectFrameworks [
              ("dnx451", None)
            ])
          ])
        ])
      ])
    ] 
  ]