NuGet package: https://www.nuget.org/packages/ContextFreeTasks/
Use ContextFreeTask struct instead of Task class (System.Threading.Tasks namespace) for return types of async methods.
private async ContextFreeTask FAsync()
{
...
}This ignores the current synchronization context.
You do not have to write ConfigureAwait(false) anymore.
In C# 7, async methods may return other types in addition to Task, Task<T> and void.
The returned type must satisfy a certain pattern. These types are called "Task-like".
The ContextFreeTask struct in this library satisfies the "Task-like" pattern and the "awaitable" pattern.
This struct ignores synchronization context at all. In other words,
awaitoperations in the methods which returnContextFreeTaskcapture no contextawaitoperations onContextFreeTaskcapture no context
For example, you can use this as following:
// All awaits in this method don't capture SynchronizationContext
private async ContextFreeTask FAsync()
{
// Whatever current context is
await Task.Delay(100);
// no context here
await Task.Delay(100);
// no context here
}
private async Task GAsync()
{
// You can await on ContextFreeTask
// ContextFreeTask don't capture current context
await FAsync();
// no context here
}This code behaves almost the same as the following:
private async Task FAsync()
{
await Task.Delay(100).ConfigureAwait(false);
await Task.Delay(100).ConfigureAwait(false);
}
private async Task GAsync()
{
await FAsync().ConfigureAwait(false);
}The ContextFreeTask struct is a thin wrapper of Task class.
public struct ContextFreeTask
{
public Task Task { get; }
}And the ContextFreeTask<T> is that of Task<T>.
public struct ContextFreeTask<T>
{
public Task<T> Task { get; }
}Those awaiters always use ConfigureAwait(false).
public struct ContextFreeTaskAwaiter : ICriticalNotifyCompletion
{
private readonly Task _value;
public void OnCompleted(Action continuation) => _value.ConfigureAwait(false).GetAwaiter().OnCompleted(continuation);
}Furthermore, those AsyncMethodBuilders always clear current synchronization context.
public struct AsyncContextFreeTaskMethodBuilder
{
private AsyncTaskMethodBuilder _methodBuilder;
public void AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
where TAwaiter : INotifyCompletion
where TStateMachine : IAsyncStateMachine
{
SynchronizationContext.SetSynchronizationContext(null);
_methodBuilder.AwaitOnCompleted(ref awaiter, ref stateMachine);
}
}
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