How Do I Properly Invoke Async Methods from the Main Method in C#?

Invoking Async Methods in Main: A Comprehensive Guide

In the realm of asynchronous programming, it's not uncommon to encounter situations where we need to call an async method directly from the Main method. Understanding how this can be achieved is crucial for leveraging the benefits of asynchronous programming.

Asynchronous Method Invocation in Main

Consider the following code snippet:

<br>public class test<br>{</p>
<pre class="brush:php;toolbar:false">public async Task Go()
{
    await PrintAnswerToLife();
    Console.WriteLine("done");
}

public async Task PrintAnswerToLife()
{
    int answer = await GetAnswerToLife();
    Console.WriteLine(answer);
}

public async Task<int> GetAnswerToLife()
{
    await Task.Delay(5000);
    int answer = 21 * 2;
    return answer;
}

}

Multiple Approaches

There are several approaches to invoking async methods from the Main method:

1. Async Main Method (C# 7.1 and Newer)

For C# 7.1 and newer versions, the Main method can be marked as async. This enables the direct use of async methods within the Main method, as seen in the following example:

<br>static async Task Main(string[] args)<br>{</p>
<pre class="brush:php;toolbar:false">test t = new test();
await t.Go();
Console.WriteLine("finished");
Console.ReadKey();

}

2. Call the "Wait" Method

For earlier versions of C#, the Wait method can be used to block the thread until the async method completes. This approach is demonstrated below:

<br>static void Main(string[] args)<br>{</p>
<pre class="brush:php;toolbar:false">test t = new test();
t.Go().Wait();
Console.WriteLine("finished");
Console.ReadKey();

}

3. OnCompleted Callback (Legacy Approach)

In certain cases, you may need to use an OnCompleted callback as seen in the initial code snippet. This approach, however, can lead to deadlocks and should be avoided if possible.

Optimal Approach

For C# 7.1 and newer, using the async Main method is the preferred approach as it simplifies the code and eliminates the need for callback-based invocation. For earlier versions of C#, the Wait method can be used, but it's important to note the potential performance implications associated with blocking the thread.

Conclusion

Invoking async methods from the Main method can be achieved through various techniques. By understanding the different approaches and their implications, you can choose the optimal solution based on your specific needs and the version of C# you're using.

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