How to add custom parameters to an event handler in C#?

In C#, you can add custom parameters in an EventHandler by creating a custom EventArgs class. Here is an example:

using System;

public class CustomEventArgs : EventArgs
{
    public string CustomParameter { get; set; }

    public CustomEventArgs(string customParameter)
    {
        CustomParameter = customParameter;
    }
}

public class MyClass
{
    public event EventHandler<CustomEventArgs> CustomEvent;

    public void OnCustomEvent(string customParameter)
    {
        CustomEvent?.Invoke(this, new CustomEventArgs(customParameter));
    }
}

public class Program
{
    public static void Main()
    {
        MyClass myClass = new MyClass();
        myClass.CustomEvent += HandleCustomEvent;

        myClass.OnCustomEvent("Hello, World!");
    }

    public static void HandleCustomEvent(object sender, CustomEventArgs e)
    {
        Console.WriteLine("Custom Event Handler invoked with parameter: " + e.CustomParameter);
    }
}

In the example above, a CustomEventArgs class was custom-defined with a CustomParameter property for storing custom parameters. Then, in the MyClass class, an EventHandler event was declared with its generic parameter specified as CustomEventArgs. When the event is triggered, a CustomEventArgs object is created using new CustomEventArgs(customParameter) and passed to the event’s triggering method, Invoke. In the event handler HandleCustomEvent, the passed custom parameter can be accessed through e.CustomParameter.