anchor.diff:  be a function of any number of parameters that returns bool or unit. In the latter case, 
    a test passes if it does not throw. The entry point to create properties is the Prop module.
   
  - In C# (or, if you prefer it, you can use this API from F# too), properties are expressed
  - more explicitly and in a more type safe way by a fluent API with as entry point the Prop class.
  + Like all of FsChek's API, there are C# counterparts for all of the F# methods described.
       
   ## Conditional Properties
   
  
positive.code: let insertWithArb x = Prop.forAll orderedList (fun xs -> ordered(insert x xs))
  Check.Quick insertWithArb
  
  (**    [lang=csharp,file=../csharp/Properties.cs,key=insertWithArb] *)
  
  (***include-output:insertWithArb***)
  
  
negative.code:     |> Prop.collect (List.length xs)
  Check.Quick insertCombined
  
  (**
      [lang=csharp,file=../csharp/Properties.cs,key=insertCollect]*)
  
  (***include-output:insertCombined***)
  
  