同步调用异步方法how-would-i-run-an-async-taskt-method-synchronously

同步调用异步方法帮助类：

public static class AsyncHelpers
{
/// <summary>
/// Execute's an async Task<T> method which has a void return value synchronously
/// </summary>
/// <param name="task">Task<T> method to execute</param>
public static void RunSync(Func<Task> task)
{
var oldContext = SynchronizationContext.Current;
var synch = new ExclusiveSynchronizationContext();
SynchronizationContext.SetSynchronizationContext(synch);
synch.Post(async _ =>
{
try
{
await task();
}
catch (Exception e)
{
synch.InnerException = e;
throw;
}
finally
{
synch.EndMessageLoop();
}
}, null);
synch.BeginMessageLoop();

SynchronizationContext.SetSynchronizationContext(oldContext);
}

/// <summary>
/// Execute's an async Task<T> method which has a T return type synchronously
/// </summary>
/// <typeparam name="T">Return Type</typeparam>
/// <param name="task">Task<T> method to execute</param>
/// <returns></returns>
public static T RunSync<T>(Func<Task<T>> task)
{
var oldContext = SynchronizationContext.Current;
var synch = new ExclusiveSynchronizationContext();
SynchronizationContext.SetSynchronizationContext(synch);
T ret = default(T);
synch.Post(async _ =>
{
try
{
ret = await task();
}
catch (Exception e)
{
synch.InnerException = e;
throw;
}
finally
{
synch.EndMessageLoop();
}
}, null);
synch.BeginMessageLoop();
SynchronizationContext.SetSynchronizationContext(oldContext);
return ret;
}

private class ExclusiveSynchronizationContext : SynchronizationContext
{
private bool done;
public Exception InnerException { get; set; }
readonly AutoResetEvent workItemsWaiting = new AutoResetEvent(false);
readonly Queue<Tuple<SendOrPostCallback, object>> items =
new Queue<Tuple<SendOrPostCallback, object>>();

public override void Send(SendOrPostCallback d, object state)
{
throw new NotSupportedException("We cannot send to our same thread");
}

public override void Post(SendOrPostCallback d, object state)
{
lock (items)
{
items.Enqueue(Tuple.Create(d, state));
}
workItemsWaiting.Set();
}

public void EndMessageLoop()
{
Post(_ => done = true, null);
}

public void BeginMessageLoop()
{
while (!done)
{
Tuple<SendOrPostCallback, object> task = null;
lock (items)
{
if (items.Count > 0)
{
task = items.Dequeue();
}
}
if (task != null)
{
task.Item1(task.Item2);
if (InnerException != null) // the method threw an exeption
{
throw new AggregateException("AsyncHelpers.Run method threw an exception.", InnerException);
}
}
else
{
workItemsWaiting.WaitOne();
}
}
}

public override SynchronizationContext CreateCopy()
{
return this;
}
}
}

使用

customerList = AsyncHelpers.RunSync<List<Customer>>(() => GetCustomers());

来源链接