Simple .NET/ASP.NET PDF document editor web control SDK

WCF is a framework for building and using remotely accessible services. It s particularly well suited to XML-based web standards, although it s not limited to these. It provides a programming model that supports many different underlying communication mechanisms; as well as supporting numerous web service standards, WCF also offers high-performance proprietary protocols that you can use in end-to-end .NET systems, and it s extensible, so support for other protocols can be added. WCF s design makes many of these details a matter of configuration you write services and clients in the same way no matter what communication mechanisms are in use. To explore WCF, we ll build a very simple instant messaging application to allow multiple users to chat with one another. So that we can focus on the communication code, the client will be a simple console application.

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As you can see from Figure 11-10, it contains a simple HTML table that contains the headers for the table. Then, under this an UpdatePanel control is placed, which contains a single label. This label will be loaded with the HTML for the rest of the table, as you will see in a moment. Although it isn t visible in the designer, this is contained within an ASP.NET Panel control that allows you to put this in a fixed dimension area with scrollbars that allow you to scroll through the data. This has two benefits. First, the header fields for the data and price will not scroll off the screen. Second, if the table has several hundred rows and is not contained in a scrollable pane like this, then it will dominate the UI, and you will need to scroll way down in the browser to see the rest of the page content. You can see it in action using the scrollbars in Figure 11-11.

Until now, you have been dealing with projects for building applications. QMake can also be used for building libraries, including static libraries, dynamic libraries, and plugins (which are a special breed of dynamic libraries). To make QMake do this, you must change the TEMPLATE variable to lib. An example of a library project is shown in Listing 15-3. The project uses the SOURCES and HEADERS variables in the same way as when building applications. TARGET and VERSION are merged to create the file name of the resulting library, which is a common way to avoid versioning problems. Because different versions of the library have different names, the problem is avoided.

We ll start with the server for our chat application If you want to build your own copy of the project as you read, open Visual Studio s New Project dialog (Ctrl-Shift-N) and in the template list on the left, select Visual C# WCF Choose the WCF Service Library project template Call the project ChatServerLibrary Ensure that the Create directory for solution checkbox is checked, and call the solution WcfChat This project will produce a DLL as its output, because the WCF Service Library project template doesn t commit to hosting the WCF service in any particular container application WCF can run inside IIS, a Windows Service, a console application, or indeed pretty much any NET application If you want to use a particular kind of host, you can just create the relevant type of project for example, instead of creating a WCF Service Library, you could create an ASP.

NET web application project if you wanted to host your WCF service in there (You can add a WCF service as a new item to an existing web project, so you don t need a WCF-specific project type) But there are a couple of benefits to this library-based template: as you ll see shortly, it provides an easy way to do simple manual testing of the service Also, it means you can host the service in multiple different host applications, which can be useful for automated testing you can test the service without having to deploy it into its intended environment Visual Studio will have added a single service to the project, called Service1 This contains some example code that does things we don t need in our chat application, so we ll ignore that.

(Feel free to delete them if you re building your own version as you read this) We ll add a new WCF Service item to the project with the Add New Item dialog, called ChatService Visual Studio adds two files to the project: ChatServicecs and IChatServicecs This reflects the fact that WCF makes a distinction between the code that implements a service, and the contract for that service..

Caution Using VERSION means that the name of your library will be altered. Don t let this confuse you.

When two systems communicate over a network, they need to agree on what information is to be sent back and forth. WCF formalizes this with what it calls contracts. So the IChatService interface added by the wizard represents a service contract. The service contract defines the operations the service offers. As Example 13-1 shows, the interface is marked with a ServiceContract attribute to make it clear that it s a contract definition.

[ServiceContract] public interface IChatService { [OperationContract] void DoWork(); }