REST-style Windows Communication Foundation (WCF) services

REST-style Windows Communication Foundation (WCF) services. These services are based on the WCF web programming model available in .Net 3.5 SP1. The starter kit also contains the full source code for all features, detailed code samples, and unit tests.
The first set of features in the starter kit is server-side features for building WCF REST services, which enable or simplify various aspects of using the REST capabilities in WCF. These include declarative caching, security, error handling, help page support, conditional PUT, push style streaming, type based dispatch and semi-structured XML support. This functionality is exercised by a set of Visual Studio templates for creating REST services such as an Atom Feed service, a REST-RPC hybrid service, a resource singleton or collection service, and an Atom Publishing Protocol service.
Preview 2 of the starter kit introduces a second set of client-side features for accessing WCF and third-party REST services from within .Net applications. The new HttpClient class provides the REST developer with a uniform extensible model for sending HTTP requests and processing HTTP responses, in a variety of formats. The new "Paste Xml as Type" Visual Studio add-in enhances the serialization support in HttpClient by generating serializable types based on XML examples or XSD schema.

 

for more information, go http://aspnet.codeplex.com

Posted in: C# and .NET| Tags: Communication Service Provider NET Windows XML WCF REST service kit rest-style set support

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Tip: jQuery AJAX calls to a WCF REST Service

WCF 3.5 includes REST functionality and one of the features of the new WCF webHttp binding is to return results in a variety of ways that are URL accessible. WCF has always supported plain URL HTTP access, but it's not been real formal and had somewhat limited functionality as parameters had to be encodable as query string parameters. With the webHttp binding there's now an official WCF protocol geared towards providing ASP.NET AJAX JSON compatibility (using WebScript behavior) as well of a slightly cleaner raw JSON implementation (basic webHttp binding).

You can return XML (default), JSON or raw data from WCF REST services. Regardless of content type, natively WCF always wants to return content in a 'wrapped' format which means that both inbound parameters and outbound results are wrapped into an object.

Let's take a look at the message format for a  REST JSON service method.

[ServiceContract(Name="StockService",Namespace="JsonStockService")]    

public interface IJsonStockService

{

    [OperationContract]          

    [WebInvoke(Method="POST",

               BodyStyle=WebMessageBodyStyle.Wrapped,

               ResponseFormat=WebMessageFormat.Json

    )]

    StockQuote GetStockQuote(string symbol);

..

The input message on the wire looks like this:

{"symbol":"MSFT"}

The response looks like this:

{"GetStockQuoteResult":

        {"Company":"MICROSOFT CP",

        "LastPrice":30.00,

        "LastQuoteTime":

        "\/Date(1208559600000-0700)\/",

        "LastQuoteTimeString":"Apr 18, 4:00PM",

        "NetChange":0.78,

        "OpenPrice":29.99,

        "Symbol":"MSFT"}

}

Notice that in both cases an object is used. For the inbound data all parameters are wrapped into an object and rather than just passing the value, the name of the parameter becomes a property in the JSON object map that gets sent to the server. This is actually quite useful - if you're just sending a raw JSON structure you could only pass a single parameter to the server - and that option is also available via the Web BodyStyle=WebMessageBodyStyle.Bare option on the service method.

The outbound result set is also wrapped into an object which is a lot less useful. This is a hold over from WCF which wraps all responses into a message result object, which usually makes sense in order to support multiple result values (ie. out parameters etc.). In a Web scenario however this doesn't really buy you much. Nevertheless if you want to pass multiple parameters to the server you have to use this wrapped format along with the result value.

Calling with jQuery

If you're using jQuery and you'd like to call a WCF REST service it's actually quite easy either with bare or wrapped messages. Bare messages are easier to work with since they skip the wrapping shown above, but as I mentioned you're limited to a single input parameter. So if your service has any complexity you'll likely want to use wrapped messages.

You can opt to either call services using the ASP.NET Ajax logic (WebScriptService behavior) or using the raw service functionality which is shown above.

To call these methods with jQuery is fairly straight forward in concept - jQuery includes both low level and highlevel methods that can call a URL and return JSON data. The two methods available are $.getJSON() which automatically parses result JSON data and $.ajax(), which is a lower level function that has many options for making remote calls and returning data.

getJSON() is useful for simple scenarios where the server returns JSON, but it doesn't allow you to pass JSON data TO the server. The only way to send data to the server with getJSON is via query string or POST data that is sent as standard POST key/value pairs. In all but the simplest scenarios getJSON() is not all that useful.

The lower level $.ajax method is more flexible, but even so it still lacks the capability to pass JSON data TO the server. So little extra work and some external JSON support is required to create JSON output on the client as well as dealing with Microsoft Ajax's date formatting.

Posted in: C# and .NET| Tags: Format Tip WCF ajax jQuery REST url webhttp json functionality content

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