How to call asynchronous method from synchronous method in C#?

How to Call Asynchronous Methods from Synchronous Methods in C#?

Are you stuck with a synchronous method and wondering how to call asynchronous methods from it? Don't worry, we've got you covered! In this blog post, we will address this common issue and provide you with easy solutions to make your code work seamlessly.

The Challenge

Let's say you have a Foo() method that is declared as public async void Foo(). Now, you want to call this asynchronous method from a synchronous method. But here comes the challenge - all the examples and documentation you've come across so far demonstrate calling async methods within other async methods. But what if your entire program is not built with async methods? Is it even possible? The answer is yes!

The Solution

Option 1: Using Task.Run()

One way to deal with this situation is by using the Task.Run() method. This method allows you to offload the execution of an asynchronous method to a background thread. Here's how you can do it:

public void SyncMethod()
{
    // Calling an asynchronous method from a synchronous method
    Task.Run(async () => await Foo()).GetAwaiter().GetResult();
}

public async Task Foo()
{
    // Your asynchronous logic goes here
    await SomeAsyncMethod();
}

By wrapping the call to Foo() inside Task.Run(), you create a new task that executes the asynchronous method in the background. The GetAwaiter().GetResult() call ensures that the synchronous method waits for the asynchronous method to complete.

Option 2: Using TaskCompletionSource

Another option to call an asynchronous method from a synchronous method is by using TaskCompletionSource. This class allows you to create a custom task and complete it manually. Here's an example:

public void SyncMethod()
{
    // Creating a custom task using TaskCompletionSource
    var taskCompletionSource = new TaskCompletionSource<bool>();
    
    Foo().ContinueWith(task => taskCompletionSource.SetResult(true));
    
    taskCompletionSource.Task.GetAwaiter().GetResult();
}

public async Task Foo()
{
    // Your asynchronous logic goes here
    await SomeAsyncMethod();
}

In this approach, we create a new TaskCompletionSource<bool> to represent the completion of our asynchronous method. We then use the ContinueWith() method to set the result of the task when Foo() completes. Finally, we wait for the task to complete by calling GetAwaiter().GetResult().

Summary

Calling asynchronous methods from synchronous methods in C# is indeed possible, despite the lack of examples in the documentation. You have learned two easy solutions to tackle this challenge:

1. Use Task.Run() to execute the asynchronous method on a background thread.

2. Utilize TaskCompletionSource to create a custom task and manually complete it.

Now, you have the knowledge and tools to make your code work seamlessly, regardless of the mixture of synchronous and asynchronous methods in your program.

Remember, in modern software development, asynchronous programming is crucial for performance and user experience. Embrace the power of asynchronous methods while keeping your codebase coherent and efficient.

Your Turn

Have you faced challenges calling asynchronous methods from synchronous methods? How did you solve them? Let us know in the comments below. We would love to hear your experiences and solutions!

So go ahead, try out these solutions in your code, and unleash the potential of asynchronous programming in your applications. Happy coding! 😄🚀