I was just listening to Don, Dave and James on the second of the Jumpstart series for the Codemasons’ Guild and the topic of communicating via WCF came up. Now typically when I build mobile apps I don’t go through all the pain of using WCF, I simply use a regular asmx web service and then use Add Web Reference to add it to my mobile project. To secure it, I just communicate over SSL. If you do want/need to use WCF on the server side, there are a couple of options to do this.
Before we jump into how you use WCF, let me point out a couple of useful powertoys:
- Windows Mobile Developer Power Toys [http://www.microsoft.com/downloads/details.aspx?FamilyID=74473fd6-1dcc-47aa-ab28-6a2b006edfe9&displaylang=en]
- Power Toys for .NET Compact Framework 3.5 [http://www.microsoft.com/downloads/details.aspx?FamilyID=c8174c14-a27d-4148-bf01-86c2e0953eab&displaylang=en]
The Power Toys for .NET CF include NetCFSvcUtil.exe which is a device equivalent of SvcUtil.exe and is needed in order generate the WCF proxy.
Firstly, you need to be aware that the .NET CF has some severe limitations when it comes to WCF. Unfortunately the only binding that is supported (excluding the much over-hyped WCF via Exchange) is basicHttpBinding. For the WCF service you want to consume you need to change it from using the default wsHttpBinding. This can be done by launching the Tools > WCF Service Configuration Editor from Visual Studio. Open the web.config file for the WCF Service project. Under Endpoints, adjust the Binding to basicHttpBinding.
Save this change and run the WCF Service.
Now to the options…..
1) The first option is to use Add Web Reference. This is by far the simplest approach as you can click Browse to: Web services in this solution. Select your service and click Add Reference.
Once you have added the reference you can call your service method the same way you would from a regular desktop application:
localhost.Service1 service = new localhost.Service1();
service.Url = service.Url.Replace("localhost", "192.168.1.2");
return service.GetData(5, true);
Note: You have to change the “localhost” host name to something that can be resolved by the device. I typically just use the ip address of the development machine. Clearly for production you will want to specify this in a configuration file or make it a configurable setting within your application.
2) The second option is to use NetCFSvcUtil.exe to generate the appropriate WCF proxy information. Start by opening up the Visual Studio command prompt (Start > Microsoft Visual Studio 2008 > Visual Studio Tools > Visual Studio 2008 Command Prompt) and adding the path to the Compact Framework power toys:
>> set path=%path%;C:Program FilesMicrosoft.NETSDKCompactFrameworkv3.5bin
Navigate to the folder where you want the proxy files to be created and then use NetCFSvcUtil. I figured this would be quite simple but it appears that somewhere between Vista SP1 and SP2 (and there are reports of this problem on Windows 7 too) a bug in NETCFSvcUtil surfaced preventing it from working.
As you can see the error message is really helpful:
Error: An error occurred in the tool.
Error: Error in the application.
Currently, there doesn’t seem to be a workaround for this. Some people have had varied success by changing the parameters and return types of the service methods. The one strategy I used that appears to work is to use a combination of SvcUtil and NetCFSvcUtil.
>> svcutil.exe c:tempWindowsMobileServicesMyDataServicesbinMyDataServices.dll
Microsoft (R) Service Model Metadata Tool
[Microsoft (R) Windows (R) Communication Foundation, Version 3.0.4506.2152]
Copyright (c) Microsoft Corporation. All rights reserved.Generating metadata files…
C:tempWindowsMobileServicesWindowsMobileServicestempuri.org.wsdl
C:tempWindowsMobileServicesWindowsMobileServicestempuri.org.xsd
C:tempWindowsMobileServicesWindowsMobileServicesschemas.microsoft.com.2003.1
0.Serialization.xsd>> netcfsvcutil.exe tempuri.org.wsd tempuri.org.xsd
Microsoft (R) .NET Compact Framework Service Model Metadata Tool
[Microsoft (R) Windows (R) Communication Foundation, Version 3.5.0.0]
Copyright (c) Microsoft Corporation. All rights reserved.Generating files…
C:tempWindowsMobileServicesWindowsMobileServicestempuri.org.cs
C:tempWindowsMobileServicesWindowsMobileServicesCFClientBase.cs
Now, include all the generated file into your mobile project. You will also need to add references to System.ServiceModel and System.Runtime.Serialization.
In order to call your service method you can now write the following:
var binding = System.ServiceModel.BasicHttpBinding();
var endpoint = System.ServiceModel.EndpointAddress("http://192.168.1.2:6323/Service1.svc");
Service1Client client = new Service1Client(new binding, new endpoint);
return client.GetData(5);
So, the question is why would you go the second option? Well if you actually look at the generated code, adding the WCF service using Add Web Reference adds a bunch of unnecessary fields. When calling the method GetData there is a second parameter called “valueSpecified” which is little more than a flag to indicate if the first parameter was specified or not. This is not required if you use the second option to generate the proxy information.