public static bool IsAwaitable(this Type type)
{
if (type == null || type == typeof(void))
{
return(false);
}
return(AwaitableInfo.IsTypeAwaitable(type, out _));
}
public static bool IsTypeAwaitable(Type type, out AwaitableInfo awaitableInfo)
{
// Based on Roslyn code: http://source.roslyn.io/#Microsoft.CodeAnalysis.Workspaces/Shared/Extensions/ISymbolExtensions.cs,db4d48ba694b9347
// Awaitable must have method matching "object GetAwaiter()"
var getAwaiterMethod = type.GetRuntimeMethods().FirstOrDefault(m =>
m.Name.Equals("GetAwaiter", StringComparison.OrdinalIgnoreCase) &&
m.GetParameters().Length == 0 &&
m.ReturnType != null);
if (getAwaiterMethod == null)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
var awaiterType = getAwaiterMethod.ReturnType;
// Awaiter must have property matching "bool IsCompleted { get; }"
var isCompletedProperty = awaiterType.GetRuntimeProperties().FirstOrDefault(p =>
p.Name.Equals("IsCompleted", StringComparison.OrdinalIgnoreCase) &&
p.PropertyType == typeof(bool) &&
p.GetMethod != null);
if (isCompletedProperty == null)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
// Awaiter must implement INotifyCompletion
var awaiterInterfaces = awaiterType.GetInterfaces();
var implementsINotifyCompletion = awaiterInterfaces.Any(t => t == typeof(INotifyCompletion));
if (!implementsINotifyCompletion)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
// INotifyCompletion supplies a method matching "void OnCompleted(Action action)"
var onCompletedMethod = typeof(INotifyCompletion).GetRuntimeMethods().Single(m =>
m.Name.Equals("OnCompleted", StringComparison.OrdinalIgnoreCase) &&
m.ReturnType == typeof(void) &&
m.GetParameters().Length == 1 &&
m.GetParameters()[0].ParameterType == typeof(Action));
// Awaiter optionally implements ICriticalNotifyCompletion
var implementsICriticalNotifyCompletion = awaiterInterfaces.Any(t => t == typeof(ICriticalNotifyCompletion));
MethodInfo unsafeOnCompletedMethod;
if (implementsICriticalNotifyCompletion)
{
// ICriticalNotifyCompletion supplies a method matching "void UnsafeOnCompleted(Action action)"
unsafeOnCompletedMethod = typeof(ICriticalNotifyCompletion).GetRuntimeMethods().Single(m =>
m.Name.Equals("UnsafeOnCompleted", StringComparison.OrdinalIgnoreCase) &&
m.ReturnType == typeof(void) &&
m.GetParameters().Length == 1 &&
m.GetParameters()[0].ParameterType == typeof(Action));
}
else
{
unsafeOnCompletedMethod = null;
}
// Awaiter must have method matching "void GetResult" or "T GetResult()"
var getResultMethod = awaiterType.GetRuntimeMethods().FirstOrDefault(m =>
m.Name.Equals("GetResult") &&
m.GetParameters().Length == 0);
if (getResultMethod == null)
{
awaitableInfo = default(AwaitableInfo);
return(false);
}
awaitableInfo = new AwaitableInfo(
awaiterType,
isCompletedProperty,
getResultMethod,
onCompletedMethod,
unsafeOnCompletedMethod,
getResultMethod.ReturnType,
getAwaiterMethod);
return(true);
}
