C# Convert non standard Event an Observable using Observable.FromEvent and the conversion function

ObservableFromEvent_NonStandard.cs

// Demo of how to convert an non-standard event into an Observable Sequence
// by using the Observable.FromEvent overload that uses a conversion Function.

 public class SomeObservableClass
 {
    public delegate void SettingChangedEventHandler(object sender, string setting);
    public event SettingChangedEventHandler SettingChanged;
 }

void Main()
{
   SomeObservableClass cls = new SomeObservableClass();

   Observable.FromEvent<SettingChangedEventHandler, string>
   ( handler_ => (sdr_, args_) => handler_(args_),
     h => cls.SettingChanged += h, h => cls.SettingChanged -= h) // Define conversion here ...
     .Subscribe(args => System.Diagnostics.Debug.WriteLine(args));
}

You can omit the sender argument to simplified, easier to understand for beginner.

public class SomeObservableClass
{
    public delegate void SettingChangedEventHandler(string setting);
    public event SettingChangedEventHandler SettingChanged;
}

void Main()
{
    SomeObservableClass cls = new SomeObservableClass();

    Observable.FromEvent<SettingChangedEventHandler, string>( 
        handler => (args) => handler(args), 
        h => cls.SettingChanged += h, 
        h => cls.SettingChanged -= h)
    .Subscribe(args => System.Diagnostics.Debug.WriteLine(args));
}