Gets a value that indicates whether the asynchronous operation completed synchronously.
Assembly: mscorlib (in mscorlib.dll)
If the synchronous completion of the call is detected in the AsyncCallback delegate, it is probable that the thread that initiated the asynchronous operation is the current thread.Notes to Implementers
Most implementers of the IAsyncResult interface will not use this property and should return false. Beginning with the .NET Framework 4.5, a task that is created with the FromAsync method will not complete if this property is not implemented correctly. See Application Compatibility in the .NET Framework 4.5.Notes to Callers
Use this property to determine if the asynchronous operation completed synchronously. For example, this property can return true for an asynchronous I/O operation if the I/O request was small.
.NET FrameworkSupported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1
.NET Framework Client ProfileSupported in: 4, 3.5 SP1
XNA FrameworkSupported in: 3.0, 2.0, 1.0
Portable Class LibrarySupported in: Portable Class Library
Supported in: Windows Phone 8.1
Supported in: Windows Phone Silverlight 8.1
Supported in: Windows Phone Silverlight 8