Asynchronous programming in C#

Asynchronous programming is a way to write code that can run multiple tasks simultaneously without blocking the main thread. This is useful for tasks that take a long time to complete, such as database queries, network requests, or file operations.

How does asynchronous programming work in C#?

The Task Parallel Library (TPL) is a set of classes and interfaces that provide support for asynchronous programming in C#.

The TPL provides a number of features for asynchronous programming, such as:

  1. Tasks: Tasks are the basic building blocks of asynchronous programming in C#. A task represents a unit of work that can be executed asynchronously.
  2. Async methods: Async methods are methods that can be run asynchronously. Async methods are declared using the async keyword.
  3. Await: The await keyword is used to suspend the execution of an async method until a task completes.
  4. TPL Dataflow: The TPL Dataflow library provides support for creating and managing data pipelines.
Example of an asynchronous method in C#
public async Task GetCustomerByIdAsync(int id) { // Get the customer from the database. var customer = await customerRepository.GetByIdAsync(id); // Return the customer. return customer; }

This method uses the async keyword to declare that it is an asynchronous method. The await keyword is used to suspend the execution of the method until the customerRepository.GetByIdAsync() method completes.

To call the asynchronous method, you would use the following code:

var customer = await GetCustomerByIdAsync(1);

The await keyword will suspend the execution of the current method until the GetCustomerByIdAsync() method completes. Once the GetCustomerByIdAsync() method completes, the customer variable will contain the customer object.

Exception Handling

You can handle exceptions in asynchronous methods using regular try-catch blocks.

public async Task HandleExceptionsAsync() { try { // Perform asynchronous operations await DoAsyncWork(); } catch (Exception ex) { Console.WriteLine($"An error occurred: {ex.Message}"); } }

Using Task.Run for CPU-Bound Operations

While async/await is ideal for I/O-bound operations, for CPU-bound tasks, you can use Task.Run to offload work to a separate thread.

public async Task CalculatePrimeAsync() { await Task.Run(() => { // Perform CPU-bound calculation var result = CalculatePrimeNumber(); Console.WriteLine($"Prime number: {result}"); }); }

When to use asynchronous programming in C#

You should use asynchronous programming in C# when you need to perform a long-running operation that could block the main thread. This could include tasks such as database queries, network requests, or file operations.


Asynchronous programming in C# is a fundamental technique for creating responsive and scalable applications. It allows you to use the full potential of multi-core processors and ensures that your applications remain responsive even when performing time-consuming operations.