An example of events with accessors and basic "thread-safety" precautions in C# (applies to several language versions) ...

EventsInCSharpExample.cs

#define DEV_BUILD
#region Using Directives
using System;
using System.Drawing;
using System.Reflection;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Diagnostics.CodeAnalysis;
#endregion
namespace GameDevNerds.Examples.CSharpEvents ;



// --------------------------------------------------

/// <summary>Simple example interface</summary>
public interface IDrawable {
#if DEBUG || DEV_BUILD
    /// <summary>Times execution speed</summary>
    Stopwatch? DebugStopwatch { get; }
#endif
    /// <summary>Run when frame begins to render</summary>
    void OnDraw( object sender, EventArgs e ) ;
} ;


// --------------------------------------------------


public abstract class EventSample: IDrawable {
#if DEBUG || DEV_BUILD
    public Stopwatch? DebugStopwatch { get; protected set; }
#endif
    
    //! Some kind of "starting drawing" event:
    public virtual void OnDraw( object sender, EventArgs e ) {
        //! Do stuff before frame gets drawn ...
    
        //! Now fire the event to subscribers:
        preDrawEvent?.Invoke( this, EventArgs.Empty ) ;
    }
    
    
    //! Declare private event:
    object objectLock = new( ) ;
    event EventHandler? preDrawEvent ;
    
    //! Create public accessor:
    public event EventHandler OnBeginDraw {
        [MethodImpl(0x100 | 0x200)]
        add { lock (objectLock) {
                //! We can log stuff, set breakpoints, etc
                //! And control what we allow to happen here ...
                preDrawEvent += value ;
            }
        }
        [MethodImpl(0x100 | 0x200)]
        remove { lock (objectLock) {
                preDrawEvent -= value ;
            }
        }
    }
}

Hopefully, this is helpful for people looking to have more control, mileage and "thread-safety" in their events and learn stronger patterns for larger and more sophisticated software ...