IObserver<TValue, TResult>
                
                
Provides a mechanism for receiving push-based notifications and returning a response.
            
                 
                
using System.
Runtime.
CompilerServices;
namespace System.
Reactive
{
    [
System.
Runtime.
CompilerServices.
NullableContext(
1)]
    
public interface IObserver<[
System.
Runtime.
CompilerServices.
Nullable(
2)] 
in TValue, [
System.
Runtime.
CompilerServices.
Nullable(
2)] 
out TResult>
    {
        
TResult OnNext(
TValue value);
        
TResult OnError(
Exception exception);
        
TResult OnCompleted();
    }
}