Accessing loosely structured data from F# and C#

Tomas Petricek ,[object Object],[object Object],Accessing loosely structured data from F# and C# http://tomasp.net/blog | @tomaspetricek

A little bit about me… ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The Problem ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What you’ll learn today ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Dynamic in C# and F# ,[object Object],[object Object],[object Object],[object Object],X ml Element element = GetElement (); int size = e lement . Attribute < int > ( "Size" );

Dynamic in C# and F# ,[object Object],[object Object],dynamic element = GetElement (); int size = e lement . Size ; let element = GetElement (); let size = e lement ? Size ;

Demo: Using WorldBank data in C#

Dynamic type in C# ,[object Object],[object Object],class DynamicWorldBank : DynamicObject { public override bool TryInvokeMember ( InvokeMemberBinder binder , object [] args , out object result) { result = /* member access for 'binder.Name' */ return true ; } } dynamic wb = new DynamicWorldBank (); dynamic regions = wb . Region ( new { PerPage = 100 });

Simple database access in F# ,[object Object],[object Object],[object Object],let getCategories() : seq < int * string > = [ for row in db . Query ? GetProducts () -> row ? ID , row ? Name ] let ( ? ) ( x : Row) ( name : string ) : ' R = x . Reader . [ name ] :?> ' R

Structure in the language ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Domain modeling in LINQ ,[object Object],[object Object],[object Object],public partial class Books { [ Column ( Storage = "_ID" , DbType = "Int" , IsPrimaryKey = true )] public int ID { get ; set ; } [ Column ( Storage = "_Title" , DbType = "VarChar(100)" )] public string Title { get ; set ; } } var q = from p in db . GetTable < Books > () select p . Title ;

Domain modeling in F# ,[object Object],[object Object],[object Object],Primitive values ,[object Object],Records ,[object Object],Discriminated unions

Nicer database access in F# ,[object Object],[object Object],[object Object],let load () : seq < Book > = let db = new DynamicDatabase ( connectionString ) db . Query ? Get Books () type Book = { ID : int ; Title : string }

Domain modeling in F# ,[object Object],type Title = Title of string type Link = Link of string type Description = Description of string /// Item consists of title, link and description type Item = Item of Title * Link * Description /// Represents channel with title (etc.) and list of items type Channel = Channel of Title * Link * Description * list < Item > /// Represents RSS feed containing a channel type Rss = Rss of Channel

Working with XML ,[object Object],[object Object],[object Object],[object Object],[object Object],let rss = StructuralXml . Load ( "http://.../feed" ) match rss . Root with | Rss ( Channel ( Title title , _ , _, items )) -> printfn "%s (%d items)" title items . Length

Demo: Accessing WorldBank data

What is a type provider? ,[object Object],[object Object],[object Object],[object Object],public interface ITypeProvider { Type [] GetTypes (); Expression GetInvokerExpression ( MethodBase method , ParameterExpression [] params ); event EventHandler Invalidate ; }

Type provider trickery ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Demo: Accessing Freebase data

Summary ,[object Object],Dynamic type or operator ,[object Object],[object Object],[object Object],Domain model ,[object Object],[object Object],[object Object],Type providers ,[object Object],[object Object],[object Object]

Discussion ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

World Bank provider details ,[object Object],[object Object],[object Object],type Runtime = static member GetValuesByCountryAndIndicator ( country : string , indicator : string ) : seq < int * float > = seq { for ( k , v ) in WorldBank . GetData [ country ; indicator ] do if not ( String . IsNullOrEmpty v ) then yield int k , float v } static member GetCountriesByRegion ( code : string ) : seq < string > = seq { for ( key , _) in WorldBank . GetCountries ( code ) -> key }

Calling PHP from C# ,[object Object],[object Object],class SampleObj { function Add ($ a , $ b ) { return $ a + $ b ; } } [ DuckType ] public interface ISampleObj { int Add ( int i1 , int i2 ); } ISampleObj so = ctx . New < ISampleObj > ( "SampleObj" ); int res = so . Add ( 18 , 26 );

Accessing loosely structured data from F# and C#

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