使用Xamarin Forms调用Web服务及相关技术疑问

Hey there! Let's work through your Xamarin.Forms questions step by step—these are super common hurdles when you're getting started, so don't stress:

1. What's the "Portable" project in tutorials/demos, and why doesn't my new project have that name? #

That "Portable" project refers to a Portable Class Library (PCL), which was the older standard for sharing cross-platform code in Xamarin.Forms. These days, Xamarin.Forms defaults to using .NET Standard Class Libraries (or sometimes Shared Projects) instead.

Your new project isn't named "Portable" because Microsoft phased out PCLs in favor of .NET Standard a few years back—they serve the same core purpose (hosting code that works across iOS, Android, and other platforms), but .NET Standard offers a more consistent, modern API surface that aligns better with current .NET development practices.

2. Do I have to create service interfaces myself? #

It depends on your app's complexity, but it's almost always a best practice:

• If you're using dependency injection (DI) (highly recommended for Xamarin.Forms apps), interfaces are non-negotiable. They let you swap implementations effortlessly—for example, you could have an IWeatherService with a real API implementation for production and a mock version for testing.
• For tiny, simple apps with no plans to scale or test, you could skip interfaces and write concrete service classes directly. But this will make your code far harder to maintain and extend as your app grows.

Think of interfaces as a contract: they define what a service does, not how it does it. This keeps your shared code clean and decoupled from platform-specific details.

3. Why can't I use the generated methods from References.cs after adding a web reference? #

There are a few common reasons for this:

• Asynchronous requirements: Most web service references (like SOAP/WCF) generate async methods (either Task-based or the older Begin/End pattern). Trying to call them synchronously can lead to deadlocks or compiler errors—make sure you're using await with the async methods.
• Missing service configuration: The generated proxy class needs to know where the web service is hosted. You might need to set the endpoint URL directly in code (e.g., new MyServiceClient().Endpoint.Address = new EndpointAddress("https://your-service-url");) or configure it in an App.config file.
• Platform permissions: On Android, you must add the <uses-permission android:name="android.permission.INTERNET" /> permission to your AndroidManifest.xml. On iOS, if your service uses HTTP (not HTTPS), you'll need to add an ATS (App Transport Security) exception for your service URL in Info.plist.
• Incorrect instantiation: You can't call the methods directly from the generated class—you need to create an instance of the service proxy first. For example:

  var serviceClient = new MyGeneratedServiceClient();
  var result = await serviceClient.GetDataAsync();
  

内容的提问来源于stack exchange，提问作者user7885142