What's New in Windows Communication Foundation 4.5
This topic discusses features new to Windows Communication Foundation (WCF) version 4.5.
WCF Simplification Features
Much work has been done to make WCF 4.5 applications easier to develop and maintain. For more information, see WCF Simplification Features.
Task-based Async Support
By default, Add Service Reference generates Task-returning async service operation methods. This is done for both synchronous and asynchronous methods. This allows you to call the service operations asynchronously using the new Task based async programming model. When you call the generated proxy method, WCF constructs a Task object to represent the asynchronous operation and returns that Task to you. The Task completes when the operation completes. When implementing an async operation you can implement it as a task-based async operation. For more information see, Synchronous and Asynchronous Operations.
Simplified Generated Configuration Files
When you add a service reference in Visual Studio or use the SvcUtil.exe tool, a client configuration file is generated. In previous versions of WCF these configuration files contained the value of every binding property even if its value is the default value. In WCF 4.5 the generated configuration files contain only those binding properties that are set to a non-default value.
For more information, see WCF Simplification Features.
WCF now has support for contract-first development. The svcutil.exe has a /serviceContract switch which allows you to generate service and data contracts from a WSDL document.
Add Service Reference from a Portable Subset Project
Portable subset projects enable .NET assembly programmers to maintain a single source tree and build system while still supporting multiple .NET platforms (desktop, Silverlight, Windows Phone, and Xbox). Portable subset projects only reference .NET portable libraries that are assemblies that can be used on any .NET platform. The developer experience is the same as adding a service reference within any other WCF client application. For more information, see Add Service Reference in a Portable Subset Project.
ASP.NET Compatibility Mode Default Changed
WCF provides ASP.NET compatibility mode to grant developers full access to the features in the ASP.NET HTTP pipeline when writing WCF services. To use this mode, you must set the
aspNetCompatibilityEnabled attribute to true in the <serviceHostingEnvironment> section of web.config. Additionally, any service in this appDomain needs to have the
RequirementsMode property on its AspNetCompatibilityRequirementsAttribute set to Allowed or Required. By default AspNetCompatibilityRequirementsAttribute is now set to Allowed. For more information, see WCF Services and ASP.NET.
New Transport Default Values
In order to simplify configuration a number of transport property default values have changed. For more information, see WCF Simplification Features.
XmlDictionaryReaderQuotas contains configurable quota values for XML dictionary readers which limit the amount of memory utilized by an encoder while creating a message. While these quotas are configurable, the default values have changed to lessen the possibility that a developer will have to set them explicitly. For more information, see WCF Simplification Features.
WCF Configuration Validation
As part of the build process within Visual Studio, WCF configuration files are now validated for attributes defined within the project. A list of validation errors or warnings is displayed in Visual Studio if the validation fails.
XML Editor Tooltips
In order to help new and existing WCF service developers to configure their services, the Visual Studio XML editor now provides tooltips for every configuration element and its properties that is part of the service configuration file.
Added support for true asynchronous streaming where the send side now does not block threads if the receive side is not reading or slow in reading thereby increasing scalability. Removed the limitation of message buffering when a client sends a streamed message to an IIS hosted WCF service. For more information, see WCF Simplification Features.
Simplifying Exposing an Endpoint Over HTTPS with IIS
An HTTPS protocol mapping has been added to simplify exposing an endpoint over HTTPS. To enable an HTTPS endpoint, ensure your website has an HTTPS binding and SSL certificate configured, and then simply enable HTTPS for the virtual directory that hosts the service. If metadata is enabled for the service, it will be exposed over HTTPS as well.
Generating a Single WSDL Document
Some third-party WSDL processing stacks are not able to process WSDL documents that have dependencies on other documents through a xsd:import. WCF now allows you to specify that all WSDL information be returned in a single document. To request a single WSDL document append "?singleWSDL" to the URI when requesting metadata from the service.
WebSockets is a technology that provides true bidirectional communication over ports 80 and 443 with performance characteristics similar to TCP. Two new bindings have been added to support communication over a WebSocket transport. NetHttpBinding and NetHttpsBinding. For more information see: System-Provided Bindings.
New Transport Default Values
The following table describes the settings that have changed and where to find additional information.
|Property||On||New Default||For more information see|
|listenBacklog||NetTcpBinding||12 * number of processors||ListenBacklog|
|2 * number of processors for transport
4 * number of processors for SMSvcHost.exe
|MaxPendingAccepts Configuring the Net.TCP Port Sharing Service|
|maxPendingConnections||ConnectionOrientedTransportBindingElement||12 * number of processors||MaxPendingConnections|
|receiveTimeout||SMSvcHost.exe||30 seconds||Configuring the Net.TCP Port Sharing Service|
Configuring WCF Services in Code
Windows Communication Foundation (WCF) allows developers to configure services using configuration files or code. Configuration files are useful when a service needs to be configured after being deployed. When using configuration files, an IT professional only needs to update the configuration file, no recompilation is required. Configuration files, however, can be complex and difficult to maintain. There is no support for debugging configuration files and configuration elements are referenced by names which makes authoring configuration files error-prone and difficult. WCF also allows you to configure services in code. In earlier versions of WCF (4.0 and earlier) configuring services in code was easy in self-hosted scenarios, the ServiceHost class allowed you to configure endpoints and behaviors prior to calling ServiceHost.Open. In web hosted scenarios, however, you don’t have access to the ServiceHost class. To configure a web hosted service you were required to create a
System.ServiceModel.ServiceHostFactory that created the ServiceHostFactory and performed any needed configuration. Starting with .NET Framework 4.5, WCF provides an easier way to configure both self-hosted and web hosted services in code. For more information, see Configuring WCF Services in Code.
WCF client applications use the ChannelFactory<TChannel> class to create a communication channel with a WCF service. Creating ChannelFactory<TChannel> instances incurs some overhead because it involves the following operations:
Constructing the ContractDescription tree
Reflecting all of the required CLR types
Constructing the channel stack
Disposing of resources
To help minimize this overhead, WCF can cache channel factories when you are using a WCF client proxy. For more information, see Channel Factory and Caching.
Compression and the Binary Encoder
Beginning with WCF 4.5 the WCF binary encoder adds support for compression. The type of compression is configured with the CompressionFormat property. Both the client and the service must configure the CompressionFormat property. Compression will work for HTTP, HTTPS, and TCP protocols. If a client specifies to use compression but the service does not support it a protocol exception is thrown indicating a protocol mismatch. For more information, see Choosing a Message Encoder.
Support has been added for a UDP transport which allows developers to write services that use "fire and forget" messaging. A client sends a message to a service and expects no response from the service.
Multiple Authentication Support
Support has been added to support multiple authentication modes, as supported by IIS, on a single WCF endpoint when using the HTTP transport and transport security. IIS allows you to enable multiple authentication modes on a virtual directory, this feature allows a single WCF endpoint to support the multiple authentication modes enabled for the virtual directory where the WCF service is hosted.
Support has been added to allow for WCF services with Internationalized Domain Names. For more information see WCF and Internationalized Domain Names.
Attribute values in configuration files for custom attributes defined in the project now support IntelliSense to facilitate working with configurations quickly and accurately.
WCF elements and attributes now have tooltips in the XML editor, to more easily and accurately identify the purpose of the element or attribute.
Paste Data as Classes
In a WCF project, data types defined in XML (such as are exposed in a service) can be pasted directly into a code page. The XML type will be pasted as a CLR type. See Generating Data Type Classes from XML for more details.
WebServiceHost and default endpoints
In Visual Studio 2010, WebServiceHost automatically created a default endpoint whether you explicitly specified an endpoint or not. In Visual Studio 2012 and later, WebServiceHost only creates a default endpoint if no endpoints are explicitly added. If your client is expecting the default endpoint you can explicitly add an endpoint and point the client to it. Alternatively, you can tell WCF to revert back to the previous behavior by adding the following setting to you application’s configuration file
<appSettings> <add key="wcf:webservicehost:enableautomaticendpointscompatability" value="true"/> </appSettings>
This interface, exposed by IChannelFactory<TChannel>, makes working with cookies on the client side much easier. When AllowCookies is set to true on the binding, you can access cookies by using the following code:
IHttpCookieContainerManager cookieManager = factory.GetProperty<IHttpCookieContainerManager>(); System.Net.CookieContainer container = cookieManager.CookieContainer;
You can then retrieve or set the cookies from the CookieContainer. When AllowCookies is set to false, you can manually retrieve the cookies using OperationContext and send it in other requests using another OperationContext or message inspector. The IHttpCookieContainerManager interface allows you to authenticate a user with a service and use the authentication cookie returned by that service to authenticate with other services.