Overview

The Microsoft.Bcl.Async library is a package designed to provide asynchronous programming models for older .NET Framework applications that do not natively support async and await keywords. Asynchronous programming helps improve application performance by enabling non-blocking tasks. This article will guide you through the proper use of the Microsoft.Bcl.Async library, offering technical explanations and examples where relevant.

Setting Up Microsoft.Bcl.Async

Installation

To get started, you will need to add the Microsoft.Bcl.Async package to your project. You can do this via the NuGet Package Manager Console:

Install-Package Microsoft.Bcl.Async

Alternatively, if you're using a project file that supports the PackageReference format, you can directly edit your .csproj file:

<PackageReference Include="Microsoft.Bcl.Async" Version="1.0.168" />

Compatibility

Microsoft.Bcl.Async supports:

• .NET Framework 4.0 and 4.5
• Silverlight 4, 5
• Windows Phone 7.5 and 8

Core Concepts

Asynchronous Programming in a Nutshell

Asynchronous programming is crucial for building responsive applications. The core concepts include:

• Tasks: Use Task or Task<T> for asynchronous operations.
• Await: Asynchronously wait for a task to complete.
• Async: Declare a method with async to allow the use of await inside it.

Why Use Microsoft.Bcl.Async?

Older versions of .NET do not support async/await natively. This package bridges the gap by extending these functionalities, allowing you to use modern asynchronous patterns in legacy systems.

Technical Implementations

Creating Asynchronous Methods

To use asynchronous methods with Microsoft.Bcl.Async, ensure you have appropriate Task-based methods.

1public async Task<string> FetchDataAsync()
2{
3    await Task.Delay(1000); // Simulate an async operation
4    return "Data";
5}

Handling Errors

When working with asynchronous code, error handling is crucial. Use try-catch blocks effectively:

1public async Task<string> SafeFetchDataAsync()
2{
3    try
4    {
5        await Task.Delay(1000); // Simulate an async operation
6        return "Data";
7    }
8    catch (Exception ex)
9    {
10        // Log or handle the exception
11        return $"Error: {ex.Message}";
12    }
13}

Working with UI Elements

Asynchronous operations often run on separate threads, so any interaction with UI elements should be marshaled back to the main thread. This is especially crucial in platforms like Silverlight and Windows Phone.

1public async void UpdateUIAsync()
2{
3    var result = await FetchDataAsync();
4    
5    // Ensuring the update is on the main UI thread
6    this.Dispatcher.BeginInvoke(() => 
7    {
8        // Update UI components here
9        textBox.Text = result;
10    });
11}

Best Practices

• Avoid Blockings: Ensure your asynchronous methods do not block the caller thread.
• Use ConfigureAwait(false): In library code, where the context isn't crucial, use this to avoid capturing the main thread context.

await SomeLibraryCallAsync().ConfigureAwait(false);

• Error Handling: Always anticipate exceptions in async code and handle them gracefully.
• Use Task-based API: When possible, prefer Task-based APIs over those using older asynchronous patterns like Begin/End patterns.

Key Points Summary

Conclusion

The Microsoft.Bcl.Async library opens the door to modern asynchronous programming, even on older .NET platforms. By understanding how to effectively implement and manage asynchronous methods, you can significantly enhance the performance and responsiveness of your applications. Use this guide as a reference to equip your projects with robust asynchronous capabilities.