Argument

[SeMartens]

Yes you can assign null to EventArgs, but not string or integer. Best way would be to derive EventArgs. Have a look here: http://msdn.microsoft.com/en-us/library/system.eventargs.aspx[^] Regards Sebastian

It's not a bug, it's a feature! Check out my CodeProject article Permission-by-aspect. Me in Softwareland.

[CPallini]

musefan wrote:

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

Had you doubts about? :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[N a v a n e e t h]

shennwooi wrote:

Can i assign some string or integer to EventArgs?

NO. If there is a good reason for doing this, create your own class which derives from EventArgs. Use implicit operator. Eg:

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);
}
}

:)

Navaneeth How to use google | Ask smart questions

[musefan]

yeah i wanted to double check it was nullable. Like i have said i dont see a use for it...

Life goes very fast. Tomorrow, today is already yesterday.

[CPallini]

A object reference is, by definition, nullable.

musefan wrote:

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

I see. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[BabyOreo]

i'm doing vsts2008 unit testing. How m i assign date to following test method? public void btnAddEntry_ClickTest() { frmMileage_Accessor target = new frmMileage_Accessor(); // TODO: Initialize to an appropriate value object sender = null; // TODO: Initialize to an appropriate value EventArgs e = null; // TODO: Initialize to an appropriate value target.btnAddEntry_Click(sender, e); //Assert.Inconclusive("A method that does not return a value cannot be verified."); }

[12Code]

use this

btnTest_Click(this, null);

to test button click.

;)*12Code

[BabyOreo]

what if i wan to test the following function? private void btnAddEntry_Click(object sender, EventArgs e) { double gas, miles; int i; string d; char c; bool validDate; // Validate date format (actual values not checked) // strip out any spaces d = ""; for (i = 0; i < txtDate.Text.Length; i++) { if (txtDate.Text.Substring(i, 1) != " ") { d += txtDate.Text.Substring(i, 1); } } txtDate.Text = d; validDate = true; // make sure date has eight characters (two are slashes remainder are numbers) if (txtDate.Text.Length != 8) { validDate = false; } else { for (i = 0; i < 8; i++) { c = Convert.ToChar(txtDate.Text.Substring(i, 1)); if (i == 2 || i == 5) { if (c != '/') { validDate = false; } } else { if (c < '0' || c > '9') { validDate = false; } } } } if (!validDate) { MessageBox.Show("Date must be in form mm/dd/yy", "Date Error", MessageBoxButtons.OK, MessageBoxIcon.Error); txtDate.Focus(); return; } // Make sure miles is greater than previous value miles = Convert.ToDouble(txtMiles.Text); if (numValues > 0) { if (miles <= odometer[numValues - 1]) { MessageBox.Show("Odometer reading less than previous value.", "Odometer Reading Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation); txtMiles.Focus(); return; } } // No zero gallons allowed gas = Convert.ToDouble(txtGallons.Text); if (gas <= 0) { MessageBox.Show("Gallons pumped must be greater than zero", "Gallons Pumped Error", MessageBoxButtons.OK, MessageBoxI

[DaveyM69]

You've had some good answers. To add to them, you can't use your derived event args for existing events unless you create your own controls derived from the original. For example, maybe you want to assign the integer value 1 to the event args passed when a form is loaded. You need to create your own EventArgs and your own Form with a new Load event and override the OnLoad method. Something like this.

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);
    }
}

}

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)
Why are you using VB6? Do you hate yourself? (Christian Graus)

[musefan]

what would you use it for?

Life goes very fast. Tomorrow, today is already yesterday.

[musefan]

as a parameter, no?

Life goes very fast. Tomorrow, today is already yesterday.

[CPallini]

Like for any other object reference: a null value simply states that the reference 'points' to no object. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[BabyOreo]

yes.wan to know how to assign a value to test method.

[musefan]

yes, im not doubting the use of it for other object types. but why would anyone need to assign null to EventArgs instance?

Life goes very fast. Tomorrow, today is already yesterday.

[CPallini]

Probably noone. Neverthless, the wise developer receiving a EventArgs reference (in the event handler), should consider the possibility of a null value. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[musefan]

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. Unless of course you pass it another EventArgs derived object but then you will need a cast so you would validate it first then.

Life goes very fast. Tomorrow, today is already yesterday.

[Henry Minute]

Sometimes, for example (admittedly a bad one) if you want to call a button click handler, you can use myButton_Click(this, null), rather than myButton.PerformClick(). Although, as you have said, why would you want to?

Henry Minute Do not read medical books! You could die of a misprint. - Mark Twain Girl: (staring) "Why do you need an icy cucumber?" “I want to report a fraud. The government is lying to us all.”

[musefan]

perhaps try creating your own eventargs class that inherits from EventArgs then you can put any properties you want to use in it and pass that to the button click handler

Life goes very fast. Tomorrow, today is already yesterday.

[musefan]

yep, that possible. But if you were testing with null then your button click handler would surely never make use of EventArgs and you would never need to check it. anyway if you want the functionality called manually then you should have it as a separate function that the button click handler also calls.

Life goes very fast. Tomorrow, today is already yesterday.

[Henry Minute]

Agreed, but since EventArgs is essentially empty, nothing that I can think of actually makes any use of it.

Henry Minute Do not read medical books! You could die of a misprint. - Mark Twain Girl: (staring) "Why do you need an icy cucumber?" “I want to report a fraud. The government is lying to us all.”