Why Does Mixing `await` and `.Result` in C# Async Operations Cause Deadlocks?

C#asynchronous operation

and The cause of the deadlock await .Result When using asynchronous operations in C#, it is important to understand the potential trap of mixed synchronization and asynchronous calls. In this example, due to the following code line, the last test hangs due to dead locks:

The reason for the deadlock

Assert.IsTrue(CheckStatus().Result); // 导致挂起

<一> is an asynchronous method that returns a Boolean type task.

When calling the task
1. , it will try to block the current thread until the task is completed. CheckStatus()
However, the current thread is the main test thread, and it is also a thread that performs asynchronous methods.
2. Result This leads to a deadlock: asynchronous method is trying to continue execution on the main thread, and the main thread is waiting for the task to complete.
<决> Solution: Avoid dead locks

In order to solve the problem of dead locks, when dealing with asynchronous methods, blocking operations must be avoided on the main thread. On the contrary, the use of <算> The operational symbol allows asynchronous methods to continue to execute on another thread and return the control to the main thread.

The following code demonstrates the correct usage of :

await <免> Avoid directly calling

await

As the best practice, avoid using

[Test]
public async Task CheckStatusTwiceResultTest()
{
    Assert.IsTrue(await CheckStatus());
    Assert.IsTrue(await CheckStatus());
}

or

directly on the task. Instead, rely on the mode to ensure that asynchronous operations are performed in non -blocking. Result Conclusion

By understanding the potential consequences of mixing synchronization and asynchronous calls, developers can effectively use the asynchronous methods in C#without encountering dead locks or performance problems. Result

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