Shared Projects in Xamarin are a powerful way to share code across multiple platform-specific projects, such as Android, iOS, and Windows. Here’s a detailed explanation of how to use Shared Projects in Xamarin:
What is a Shared Project?
A Shared Project contains code files and assets that can be included in any project that references them. Unlike other project types, Shared Projects do not produce compiled output on their own. Instead, the code within a Shared Project is compiled as part of each referencing project, allowing for platform-specific customizations using compiler directives.
Setting Up a Shared Project
Creating a Shared Project:
In Visual Studio, right-click on your solution in Solution Explorer.
Select Add > New Project.
Choose Shared Project from the list of project templates.
Name your project and click Create.
Adding Code to the Shared Project:
Add your common C# code files to the Shared Project. These files will be shared across all the platform-specific projects that reference this Shared Project.
Referencing the Shared Project:
In each platform-specific project (e.g., Xamarin.Android, Xamarin.iOS, Xamarin.UWP), right-click on the project in Solution Explorer.
Select Add > Reference.
In the Reference Manager, select the Shared Project you created and click OK.
Using Compiler Directives
Shared Projects allow you to include platform-specific code using compiler directives. This is useful for incorporating functionality that is specific to a particular platform.
Example:
public void ShowMessage()
{
#if __ANDROID__
Toast.MakeText(Android.App.Application.Context, "Hello from Android", ToastLength.Short).Show();
#elif __IOS__
var alert = new UIAlertView("Hello", "Hello from iOS", null, "OK", null);
alert.Show();
#elif WINDOWS_UWP
var dialog = new Windows.UI.Popups.MessageDialog("Hello from UWP");
await dialog.ShowAsync();
#endif
}
Benefits of Shared Projects
Code Reuse: Shared Projects allow you to write common code once and use it across multiple platform-specific projects.
Platform-Specific Customization: Using compiler directives, you can include platform-specific code within the shared codebase.
Simplified Project Structure: Shared Projects help maintain a clean and organized project structure by centralizing common code.
Disadvantages of Shared Projects
No Compiled Output: Shared Projects do not produce a compiled assembly. The code is compiled as part of each referencing project.
Limited Refactoring Support: Refactoring tools may not fully support code within inactive compiler directives, potentially leading to missed updates.
Example Solution Structure
A typical solution using Shared Projects might look like this:
