Xamarin Forms Creating and Using Dependency Services Step by step Implementation and Top 10 Questions and Answers
 Last Update: April 01, 2025      15 mins read      Difficulty-Level: beginner

Xamarin.Forms Creating and Using Dependency Services

Xamarin.Forms offers a powerful feature called "Dependency Services" that enables developers to call native platform-specific code from shared code. This is particularly useful when you need to use platform-specific APIs, such as accessing the device's GPS, making a phone call, or interacting with the file system, while maintaining a shared codebase across multiple platforms. Here, we'll delve into the details of creating and using Dependency Services in Xamarin.Forms.

Understanding Dependency Services

Dependency Services act as a broker between your shared code (typically in a PCL or .NET Standard library) and the platform-specific code. When you require platform-specific functionality, you define an interface in your shared code and implement that interface in each of your platform-specific projects. Dependency Service then handles the invocation of the correct platform implementation.

Steps to Create and Use Dependency Services

  1. Define an Interface in the Shared Code

    Start by defining an interface in your shared code that represents the functionality you want to expose. This interface will be implemented in each platform-specific project.

    public interface IMyDependency
{
    void PerformAction();
}

  2. Register the Dependency Implementation with Dependency Service

    You need to register the implementation of the interface in each platform-specific project. This registration tells the DependencyService which implementation to use for a particular platform.

    • Android:

      [assembly: Xamarin.Forms.Dependency(typeof(MyDependencyImplementation))]

      public class MyDependencyImplementation : IMyDependency
{
    public void PerformAction()
    {
        // Android-specific code goes here
    }
}

    • iOS:

      [assembly: Xamarin.Forms.Dependency(typeof(MyDependencyImplementation))]

      public class MyDependencyImplementation : IMyDependency
{
    public void PerformAction()
    {
        // iOS-specific code goes here
    }
}

    • UWP:

      [assembly: Xamarin.Forms.Dependency(typeof(MyDependencyImplementation))]

      public class MyDependencyImplementation : IMyDependency
{
    public void PerformAction()
    {
        // UWP-specific code goes here
    }
}

  3. Consume the Dependency Service from Shared Code

    Once the implementations are registered, you can use the DependencyService class from your shared code to call the platform-specific functionality.

    public class MySharedCode
{
    public void ExecuteAction()
    {
        var dependency = DependencyService.Get<IMyDependency>();
        dependency.PerformAction();
    }
}

Important Information

  • Thread Safety: Platform-specific dependencies might execute on different threads. Ensure that your implementations respect the threading model of the platform.

  • Error Handling: Platform-specific code can fail or throw exceptions. Always wrap calls to DependencyService.Get<> in try-catch blocks to handle any exceptions that may occur.

  • Assembly Attributes: The assembly: Xamarin.Forms.Dependency attribute is crucial for registering the implementation. If this attribute is not present, DependencyService.Get<> will return null.

  • Conditional Compilation: In some cases, you might need to provide different implementations based on the build configuration or other settings. Use preprocessor directives or other conditional compilation techniques to manage these scenarios.

  • Platform-Specific Considerations: When writing platform-specific code, always consult the official documentation for that platform. This includes APIs, permissions, and best practices.

Example Use Cases

  • Opening a Web Browser: Use a dependency service to open a web browser on the device.

  • Accessing Native File Picker: Provide a consistent file picker experience across platforms.

  • Sending SMS: Implement platform-specific logic to send SMS messages.

Conclusion

Dependency Services in Xamarin.Forms are a powerful mechanism for integrating platform-specific functionality seamlessly into your shared code. By following the steps outlined above and being mindful of the important considerations, you can effectively leverage this feature to create rich and robust mobile applications that feel native on every platform.

By using Dependency Services, you can write less platform-specific code, reduce redundancy, and maintain cleaner and more maintainable codebases. It's another testament to the flexibility and power of Xamarin.Forms in enabling cross-platform mobile development.

Xamarin Forms Creating and Using Dependency Services: A Step-by-Step Guide for Beginners

Xamarin.Forms is a powerful framework that allows developers to build cross-platform mobile applications with a single codebase. One of the key features of Xamarin.Forms is Dependency Services, which provides a way to call platform-specific APIs from shared code. In this guide, we'll explore how to create and use Dependency Services in Xamarin.Forms, step-by-step, using practical examples.

Table of Contents

  1. Understanding Dependency Services
  2. Setting Up Your Project
  3. Creating the Interface
  4. Implementing the Interface on Each Platform
  5. Setting Route and Running the Application
  6. Data Flow Through Dependency Services
  7. Conclusion

1. Understanding Dependency Services

Dependency Services in Xamarin.Forms allow you to call platform-specific APIs from your shared code. This is particularly useful when you need to perform actions that are unique to a specific platform, such as accessing device sensors, file systems, or specific hardware features.

Example Use Case

Suppose you want to play a specific sound when a user taps a button. This sound might differ slightly between Android and iOS. You can create a Dependency Service to handle this functionality, allowing you to play different sounds on each platform without changing the shared code.

2. Setting Up Your Project

Before creating your Dependency Service, you need to set up your Xamarin.Forms project.

  1. Open Visual Studio and create a new Xamarin.Forms project.
  2. Choose the Blank App (Xamarin.Forms) template.
  3. Name your project, for example, "DependencyServiceExample".

3. Creating the Interface

The first step in creating a Dependency Service is to define an interface that will be implemented across all platforms.

  1. Add a new folder in your shared project called Services.
  2. Add a new interface within this folder and name it IAudioService. Define a method, for instance, PlaySound.
// Services/IAudioService.cs
namespace DependencyServiceExample.Services
{
    public interface IAudioService
    {
        void PlaySound();
    }
}

4. Implementing the Interface on Each Platform

Now that you have the interface, you need to implement it on each platform.

Android Implementation

  1. Add a new class to the Services folder in your Android project, and name it AudioService.
  2. Implement the IAudioService interface.
// Android/Services/AudioService.cs
using Android.Media;
using DependencyServiceExample.Services;
using Xamarin.Forms;

[assembly: Dependency(typeof(AudioService))]
namespace DependencyServiceExample.Droid.Services
{
    public class AudioService : IAudioService
    {
        public void PlaySound()
        {
            var player = MediaPlayer.Create(Android.App.Application.Context, Resource.Raw.sound);
            player.Start();
        }
    }
}
  • Note: Make sure to add an audio file to the Resources/raw directory in your Android project named sound.mp3.

iOS Implementation

  1. Add a new class to the Services folder in your iOS project, and name it AudioService.
  2. Implement the IAudioService interface.
// iOS/Services/AudioService.cs
using AVFoundation;
using DependencyServiceExample.Services;
using Xamarin.Forms;

[assembly: Dependency(typeof(AudioService))]
namespace DependencyServiceExample.iOS.Services
{
    public class AudioService : IAudioService
    {
        public void PlaySound()
        {
            var pathToAudioFile = "sound.mp3";
            var url = NSBundle.MainBundle.GetUrlForFilename(pathToAudioFile);
            var player = AVAudioPlayer.FromUrl(url);
            player.Play();
        }
    }
}
  • Note: Make sure to add an audio file named sound.mp3 to your iOS project.

5. Setting Route and Running the Application

Now that you have your Dependency Service set up, let's use it in your application.

  1. Open the MainPage.xaml file in your shared project.
  2. Add a button to the XAML. This button will trigger the PlaySound method.
<!-- MainPage.xaml -->
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="DependencyServiceExample.MainPage">
    <StackLayout>
        <Button Text="Play Sound"
                Clicked="OnPlaySoundClicked"
                HorizontalOptions="Center"
                VerticalOptions="CenterAndExpand" />
    </StackLayout>
</ContentPage>
  1. Open the MainPage.xaml.cs file.
  2. Handle the button click to call the PlaySound method from the Dependency Service.
// MainPage.xaml.cs
using DependencyServiceExample.Services;
using Xamarin.Forms;

namespace DependencyServiceExample
{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
        }

        private void OnPlaySoundClicked(object sender, EventArgs e)
        {
            IAudioService audioService = DependencyService.Get<IAudioService>();
            audioService.PlaySound();
        }
    }
}

6. Data Flow Through Dependency Services

When the user taps the "Play Sound" button:

  • The OnPlaySoundClicked method is triggered.
  • The DependencyService.Get<IAudioService>() method retrieves the platform-specific IAudioService implementation.
  • The PlaySound method is invoked on the retrieved IAudioService instance.
  • Depending on the platform (Android or iOS), the appropriate PlaySound method is executed, playing the respective sound file.

7. Conclusion

In this guide, we learned how to create and use a Dependency Service in Xamarin.Forms. We started by understanding the concept of Dependency Services and then walked through the process of setting up a project, creating an interface, implementing the interface on each platform, and integrating it into the application. By following these steps, you can leverage platform-specific functionalities from your shared C# code, making your Xamarin.Forms applications more powerful and flexible.

By using Dependency Services, you can easily manage and execute platform-specific tasks, ensuring that your users have a seamless and consistent experience across different mobile platforms. Happy coding!

Certainly! Here’s a detailed guide on "Top 10 Questions and Answers on Creating and Using Dependency Services in Xamarin.Forms":

1. What is a Dependency Service in Xamarin.Forms?

Answer: A Dependency Service in Xamarin.Forms is a service that facilitates the access to platform-specific functionality from shared code. It allows you to call platform-specific APIs from a shared codebase by abstracting the platform-specific code. This is particularly useful when you need to interact with hardware or use specific platform features that are not available in Xamarin.Forms.

2. How do you define a Dependency Service?

Answer: To define a Dependency Service, you first need to create an interface in the shared project that represents the operations you wish to perform. Then, you implement this interface in each platform-specific project. Here's an example:

Shared Project:

public interface IDeviceOrientationService
{
    DeviceOrientation GetOrientation();
}

Android Project:

[assembly: Dependency(typeof(DeviceOrientationService))]
namespace YourNamespace.Droid
{
    public class DeviceOrientationService : IDeviceOrientationService
    {
        public DeviceOrientation GetOrientation()
        {
            IWindowManager windowManager = Android.App.Application.Context.GetSystemService(Context.WindowService).JavaCast<IWindowManager>();
            SurfaceOrientation orientation = windowManager.DefaultDisplay.Rotation;
            bool isLandscape = orientation == SurfaceOrientation.Rotation90 ||
                               orientation == SurfaceOrientation.Rotation270;
            return isLandscape ? DeviceOrientation.Landscape : DeviceOrientation.Portrait;
        }
    }
}

iOS Project:

[assembly: Dependency(typeof(DeviceOrientationService))]
namespace YourNamespace.iOS
{
    public class DeviceOrientationService : IDeviceOrientationService
    {
        public DeviceOrientation GetOrientation()
        {
            UIInterfaceOrientation orientation = UIApplication.SharedApplication.StatusBarOrientation;
            bool isLandscape = orientation == UIInterfaceOrientation.LandscapeLeft ||
                               orientation == UIInterfaceOrientation.LandscapeRight;
            return isLandscape ? DeviceOrientation.Landscape : DeviceOrientation.Portrait;
        }
    }
}

3. How do you register a Dependency Service?

Answer: You register a Dependency Service by using the [assembly: Dependency(typeof(T)) attribute above the implementation class. This attribute indicates to Xamarin what class to use for that particular service when running on the given platform.

Example:

[assembly: Dependency(typeof(DeviceOrientationService))]

4. How do you resolve a Dependency Service in your shared code?

Answer: To resolve a Dependency Service in your shared code, you need to use the DependencyService.Get<T>() method. This method returns an instance of the platform-specific implementation of the requested service.

Example:

var deviceOrientation = DependencyService.Get<IDeviceOrientationService>().GetOrientation();

5. Can a Dependency Service have constructors with parameters?

Answer: A Dependency Service cannot have constructors with parameters because the DependencyService.Get<T>() method does not support dependency injection with parameters. The service must have a default public constructor.

Workaround: If your service requires parameters, you can resolve the service first and then manually invoke methods that require those parameters:

var service = DependencyService.Get<IYourService>();
service.Initialize(someParameter);

6. How do you handle exceptions in a Dependency Service?

Answer: When dealing with platform-specific code, it's essential to handle exceptions appropriately to ensure the application remains responsive and user-friendly.

Example:

try
{
    var result = DependencyService.Get<IYourService>().ExecuteSomeOperation();
}
catch (Exception ex)
{
    // Log or display error
    Debug.WriteLine($"Error: {ex.Message}");
}

7. What are best practices for using Dependency Services?

Answer:

  • Keep Interfaces Simple: Interfaces should be simple and focused on a single responsibility.
  • Use Platform-Specific Features: Leverage platform-specific features by using Dependency Services.
  • Handle Resource Cleanup: Ensure that your services perform proper resource cleanup (e.g., closing database connections).
  • Test Thoroughly: Comprehensive testing is necessary to ensure platform-specific code behaves as expected.
  • Consider Alternatives: Sometimes, using a platform-specific library or custom renderer might be more appropriate.

8. Can Dependency Services be used for UI elements?

Answer: Dependency Services are not ideal for interacting directly with UI elements. Instead, use Xamarin.Forms controls or platform renderers for UI customization. Dependency Services are better suited for accessing platform-specific features that are not exposed via Xamarin.Forms.

9. How do you update UI from a Dependency Service?

Answer: To update the UI from a Dependency Service, you should typically perform the UI update in the shared code, not within the service itself. Use techniques like events, MessagingCenter, or RelayCommand to notify your shared code components about the changes performed by the Dependency Service.

Example using MessagingCenter:

// In Dependency Service
MessagingCenter.Send<object>(this, "OrientationChanged", orientation);

// In Shared Code
MessagingCenter.Subscribe<object, DeviceOrientation>
(
    this,
    "OrientationChanged",
    (sender, orientation) => {
        // Update UI
        Device.BeginInvokeOnMainThread(() =>
        {
            // Update your UI here
        });
    }
);

10. Is it possible to use asynchronous operations in a Dependency Service?

Answer: Yes, it's possible to use asynchronous operations in a Dependency Service. This is often beneficial for long-running tasks to avoid blocking the UI thread.

Example:

public interface IFileService
{
    Task<bool> SaveTextAsync(string filename, string text);
}

[assembly: Dependency(typeof(FileService))]
namespace YourNamespace.Droid
{
    public class FileService : IFileService
    {
        public async Task<bool> SaveTextAsync(string filename, string text)
        {
            try
            {
                var documentsPath = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDownloads).Path;
                var filePath = Path.Combine(documentsPath, filename);
                using (var writer = new StreamWriter(filePath))
                {
                    await writer.WriteAsync(text);
                }
                return true;
            }
            catch
            {
                return false;
            }
        }
    }
}

Using the service:

var success = await DependencyService.Get<IFileService>().SaveTextAsync("MyFile.txt", "Sample text.");

By understanding and effectively utilizing Dependency Services, you can enhance your Xamarin.Forms application with platform-specific features while maintaining a clean and maintainable codebase.