This sample shows how to consume a web service method from F# by simply posting the parameters as a query string.

Below is the F# code to consume a web method called GetNthPrime which takes a parameter index (0 based) and returns the prime number at that index:

        open System.Text
        open System.Net
        open System.IO
        open System.Xml


        /// Returns response of HTTP post
        let HttpPost (url:string) (postData:string) =
                let request = WebRequest.Create(url) in
                request.Method <- WebRequestMethods.Http.Post;        
                request.ContentType <- "application/x-www-form-urlencoded";


                let bytes = Encoding.ASCII.GetBytes(postData) in
                request.ContentLength <- Int64.of_int bytes.Length;


                let stream = request.GetRequestStream() in
                stream.Write(bytes,0,bytes.Length);
                stream.Close();


                let response = request.GetResponse(  ) in        
                let reader = new StreamReader( response.GetResponseStream() ) in
                reader.ReadToEnd()


        /// Reads Nth Prime from web service        
        let GetNthPrime n =
                let queryString = (sprintf "index=%d" n) in
                let url = "http://localhost/Prime/service.asmx/GetNthPrime" in
                let response = HttpPost url queryString in
                System.Diagnostics.Debug.WriteLine( response  );
                // Read (XML) HTTP response
                let reader = new XmlTextReader( new StringReader(response) ) in
                ignore( reader.Read() );
                ignore( reader.Read() );
                ignore( reader.Read() );
                let result = reader.ReadElementContentAsInt() in
                result


        do let prime = GetNthPrime 2 in System.Diagnostics.Debug.WriteLine(prime)

The following code fragment represents the C# web service's web method to consume; from Visual Studio create a new web service project in a virtual directory called Prime and replace the generated example method with this:

    [WebMethod]
    public int GetNthPrime(int index)
    {
        int value = 2;
        int i = 0;
        while (i < index)
        {
            ++value;
            ++i;
            while (!IsPrime(value)) ++value;            
        }
        return value;
    }


    private static bool IsPrime(int value)
    {
        int end = (int)Math.Ceiling(Math.Sqrt((double)value));
        for (int i = 2; i <= end; i++)
        {
            if (value % i == 0) return false;
        }
        return true;
    }