Styjun

Related: https://stackoverflow.com/a/17451872/3485263

I have a class which implements INotifyPropertyCHanged. Several instances of System.Windows.Forms.Binding exist which bind its properties to those of some Controls in a Windows Forms application.

public class Device : INotifyPropertyChanged
{
 public event PropertyChangedEventHandler PropertyChanged;

 void OnPropertyChanged(string property_name)
 
 if (PropertyChanged != null) // if there are any subscribers 
 PropertyChanged.Invoke(this, new PropertyChangedEventArgs(property_name));
 

 public bool connected get; set;
...

The binding occurs in the form class as follows:

button_Reboot.DataBindings.Add("Enabled", _device, "connected", false,
 DataSourceUpdateMode.Never);

The problem with this code is that the OnPropertyChanged handler and the form code appear to be working in different threads. This is because the _device is subscribed to the events of an encapsulated SerialPort instance and updates its properties on events raised by the serial port, which appears to be happening in another thread. So I get the InvalidOperationException saying that the control is accessed from a thread other than the thread it was created on.

I changed my code according to this answer. The comments to that answer contain the description of my issue as well.

void OnPropertyChanged(string property_name)

 var handler = PropertyChanged;
 if (handler != null)
 
 var e = new PropertyChangedEventArgs(property_name);
 foreach (PropertyChangedEventHandler h in handler.GetInvocationList())
 
 var synch = h.Target as ISynchronizeInvoke;
 if (synch != null && synch.InvokeRequired)
 synch.Invoke(h, new object[] this, e );
 else
 h(this, e);
 
 

The author of that answer expected h.Target to be a Control, but in my case it turns out to be a System.ComponentModel.ReflectPropertyDescriptor, some Runtime type which I observed during debugging. That type does not implement ISynchronizeInvoke and this causes synch to be null, which leads to the exception being thrown anyway because the control method is just called directly instead of being invoked synchronously.

My question is whether I can make my OnPropertyChanged handler access the Control's PropertyChangedEventHandler using the Control's ISynchronizeInvoker interface. I target .NET 4.6.2 and I'm using Visual Studio 2013.