Introduction

Portable Class Library (PCL) allows developers to create libraries that work across various .NET platforms. When using PCL, one might encounter configurations and settings that influence how asynchronous operations are handled. One such configuration is the setting to disable task-based asynchronous operations in the PCL service reference. This article provides a deep dive into what this setting means, its implications, and how developers can work with it.

What is Task-Based Asynchronous Operation?

Task-based asynchronous operations are a pattern in .NET that leverage the Task Parallel Library (TPL) to perform work asynchronously. This pattern uses the Task and Task<T> types to represent asynchronous operations and typically involves the use of the async and await keywords in C#. This approach simplifies the process of writing asynchronous code by allowing developers to write code that reads like synchronous code but provides the benefits of non-blocking operations.

Key Features

• Simplifies asynchronous programming.
• Reduces the complexity of error handling.
• Makes it easier to compose multiple asynchronous operations.

Implications of Disabling Task-Based Asynchronous Operations

When task-based asynchronous operations are disabled in a PCL service reference, the service client generated does not provide methods that return Task or Task<T>. Instead, the older event-based or IAsyncResult patterns are used for async communication. Here are some implications and examples:

Impact on Code Structure

Without task-based operations, developers need to subscribe to events or use callback methods instead of using await and async. This can result in more complex code structures:

1// When task-based async operations are disabled
2
3// Using Event-based Asynchronous Pattern (EAP)
4serviceClient.SomeOperationCompleted += (sender, e) =>
5{
6    if (e.Error != null)
7    {
8        // Handle error
9    }
10    else
11    {
12        var result = e.Result;
13        // Use the result
14    }
15};
16
17serviceClient.SomeOperationAsync(parameters);

1// When task-based async operations are enabled
2
3// Using Task-based Asynchronous Pattern (TAP)
4try
5{
6    var result = await serviceClient.SomeOperationAsync(parameters);
7    // Use the result
8}
9catch (Exception ex)
10{
11    // Handle error
12}

Compatibility Considerations

• Target Framework: Some profiles in PCL do not support the Task Parallel Library, necessitating the use of older async patterns.
• Legacy Systems: Projects depending on legacy systems or libraries that lack support for TPL will find the need to disable task-based operations.
• Dependency Constraints: External dependencies and third-party libraries that do not expose task-based asynchronous interfaces might require disabling this feature.

Configuring PCL Service Reference

To configure async operations in a PCL project, one can modify the service reference settings. This is usually done in the service reference configuration UI within Visual Studio or by manually editing the .svcmap file associated with the reference.

Configuration via Visual Studio

1. Right-click on the service reference in the Solution Explorer.
2. Select "Configure Service Reference...".
3. Check or uncheck “Generate task-based operations” as necessary.

Configuration Example

1<ServiceReference>
2  <!-- Disable task-based async operations -->
3  <GenerateAsynchronousOperations>false</GenerateAsynchronousOperations>
4</ServiceReference>

Advantages and Disadvantages of Disabling TAP

Conclusion

Understanding when and why to disable task-based asynchronous operations in PCL service references is vital for developers working across various .NET platforms or dealing with legacy systems. While the task-based pattern offers significant advantages in terms of simplicity and readability, there are cases where alternative patterns might be necessary due to compatibility constraints or existing code dependencies. Developers should evaluate their specific framework profiles and project needs before toggling this setting.