C#

musefan wrote:

shennwooi wrote:
EventArgs e = null;
This appears to work.

musefan wrote:

Like i have said i dont see a use for it...

musefan wrote:

well EventArgs does not have any useful information so you wouldn't need to check if its null or not as you would never use the reference

shennwooi wrote:

Can i assign some string or integer to EventArgs?

class MyEventArgs : EventArgs
{
    string name;
    public string Name { get { return name; } }

    public MyEventArgs(string name)
    {
        this.name = name;
    }

    public static implicit operator MyEventArgs(string str)
    {
        return new MyEventArgs(str);
    }
}

class Program
{
    static void Main(string[] args)
    {
        MyEventArgs ar = "hello";
        Console.WriteLine(ar.Name);
    }
}

btnTest_Click(this, null);

*12Code

private void btnAddEntry_Click(object sender, EventArgs e) {
    string s;
    double result=calculate(out s);
    if (s==null) textBox.Text="The result is "+result;
    else MessageBox.Show(s);
}

private double calculate(out string message) {
    message=null;
    double result=...;
    if (...) message="Something went wrong";
    ...
    return result;
}

using System;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : IntForm
    {
        public Form1()
        {
            InitializeComponent();
            this.Load += new System.EventHandler<inteventargs>(Form1_Load);
        }

        private void Form1_Load(object sender, IntEventArgs e)
        {
            Console.WriteLine(e.Value);
        }
    }

    public class IntEventArgs : EventArgs
    {
        private int _Value;

        public IntEventArgs(int value)
        {
            _Value = value;
        }
        public IntEventArgs() : this(0) { }

        public static implicit operator IntEventArgs(int value)
        {
            return new IntEventArgs(value);
        }

        /// <summary>
        /// Gets the System.Int32 value held by this IntEventArgs instance.
        /// </summary>
        public int Value
        {
            get { return _Value; }
        }
    }

    public class IntForm : Form
    {
        /// <summary>
        /// Occurs before a form is displayed for the first time.
        /// </summary>
        public new event EventHandler<IntEventArgs> Load;

        protected override void OnLoad(EventArgs e)
        {
            EventHandler<IntEventArgs> eh = Load;
            if (eh != null)
                eh(this, 1);
        }
    }
}