C# Discussion Boards - CodeProject

6-Jul-03 9:08

Can I send data through the parallel port in C#?

/\ |_ E X E GG

Working with events

stonee746-Jul-03 7:23

stonee74

6-Jul-03 7:23

Hi there,

I would like to notify my app if a socketconnection is broken.
I tried to use a self created event, with wich i want to notify an upper class in such a case.
The problem is i receive a unhandled exception of type 'System.MissingMethodException'...
Why? What Am i doing wrong and what means this error?

Thanks a lot,
stonee

	internal delegate void ConnectionHandler(SocketException se);<br />
............<br />
<br />
	public class Control<br />
	{<br />
	<br />
<br />
		internal event ConnectionHandler OnConnectionProblem;<br />
<br />
................<br />
<br />
<br />
	public Control() <br />
		{<br />
			OnConnectionProblem+=new ConnectionHandler(ESControl_OnConnectionProblem);<br />
....................<br />
<br />
<br />
			catch(SocketException se)<br />
			{<br />
				/<br />
				MessageBox.Show (se.Message );<br />
				try<br />
				{<br />
					OnConnectionProblem(se);<br />
				}<br />
				catch(MissingMethodException mme)<br />
				{<br />
				MessageBox.Show(mme.Message+"::"+mme.InnerException);<br />
				}

Re: Working with events

Jim Stewart6-Jul-03 8:24

Jim Stewart

6-Jul-03 8:24

Here's the problem:
stonee74 wrote:
OnConnectionProblem+=new ConnectionHandler(ESControl_OnConnectionProblem);
There's no method ESControl_OnConnectionProblem

Here's how I would do it:

//	this defines the event delegate
public delegate void ConnectionHandler(object sender, SocketException se);
//	this keeps all event arguments
public class ConnectionProblemEventArgs
{
	private SocketException m_SocketException;
	public ConnectionProblemEventArgs(SocketException se)
	{
		SocketException = se;
	}
	public SocketException SocketException
	{
		get
		{ return m_SocketException; }
	}
}		
public class EsControl
{
	// here's the event definition
	public event ConnectionHandler ConnectionProblem;
	
	// this raises the event
	public virtual void OnConnectionProblem(SocketException se)
	{
		if (ConnectionProblem != null)
			ConnectionProblem (this, new ConnectionProblemEventArgs (se));
	}
	
	private DoSomethingWithSocket()
	{
		try
		{
			...
		}
		catch(SocketException se)
		{
			// raise the event
			OnConnectionProblem (se);
		}
	}
}
public class EventListner
{
	public EventListner(EsControl esControl)
	{
		// subscribe to event here
		EsControl.ConnectionProblem += new ConnectionHandler (ESControl_ConnectionProblem);
	}
	
	private void ESControl_ConnectionProblem(object sender, ConnectionProblemEventArgs e)
	{
		// Handle event here
	}
}

α.γεεκ

Fortune passes everywhere.
Duke Leto Atreides

Re: Working with events

stonee746-Jul-03 10:29

stonee74

6-Jul-03 10:29

thanks,

I'm sure this will work.
I have in my original class a method definition.
I still cannot understand the errormessage..

		private void ESControl_OnConnectionProblem()<br />
		{<br />
<br />
		}

thanks for all inputs.

regards,
stonee

Adding multiple forms

FDL5-Jul-03 23:46

FDL

5-Jul-03 23:46

In Visual Basic, I can add multiple forms in a project and have a button (or other form controls) from one form bring up another form just by using the name of the form that I want to load followed by the Show method. For example,

formName.Show, secondForm.Show, or anotherForm.Show

Now is there a way to do something like this in C#?

Nick Parker6-Jul-03 2:10

Nick Parker

6-Jul-03 2:10

FDL wrote:
Now is there a way to do something like this in C#?

You have to create an instance of the object you want to 'show'. Here is an example, About is the name of the form, ab is the name of the instance of About.

About ab = new About();
ab.Show();

-Nick Parker

FDL8-Jul-03 11:42

FDL

8-Jul-03 11:42

Nick,

Thank you very much for your reply.

This is strange because I was doing something like what you did but it didn't work. Oh well, it works now. I must've just typed something wrong.

I really appreciate your help.

James T. Johnson6-Jul-03 4:12

James T. Johnson

6-Jul-03 4:12

Nick pointed you in the right direction for C# but I want to comment on the VB side of things.

While VB allows you to do that, it isn't a very good idea to do it! The problem becomes evident when you have forms that become intertwined. In one application I made there was a relationship between clients and dealerships.

Using the formName.Show method worked fine until you opened up a client, then opened up the dealership from the client, and finally tried to open another client. You would get an error!

Instead, the proper way to do it is very similar to the C# way of doing it.

(Its been a few years since I've done VB6 so pardon any typos Smile | :)

)

Dim myForm As New formName
myForm.Show

James

"I despise the city and much prefer being where a traffic jam means a line-up at McDonald's"
Me when telling a friend why I wouldn't want to live with him

Displaying a second user control in a form

FDL8-Jul-03 11:56

FDL

8-Jul-03 11:56

James,

Thanks for the advice. It is something that I'll definitely keep in mind and in my notes.

Francis

frogb0x5-Jul-03 19:33

frogb0x

5-Jul-03 19:33

I'm having a problem making a User Control display upon a form in C#.

My form starts off with a single UC on it. Its called UCInit. UCInit contains some text and a couple of buttons. When one of the buttons is clicked, I want UCInit to remove itself from the form, and a second User Control, called UCCreate, to appear.

I can get rid of the first UserControl, but UCCreate never appears. This is my code so far for when the button in UCInit is clicks:

private void btnCreate_Click(object sender, System.EventArgs e)
{
this.Hide();
UCCreate newPanel = new UCCreate();
newPanel.Location = new Point (376, 8);
newPanel.Show();
}

UCInit removes itself but the instance of UCCreate never shows itself. What am I doing wrong?

J. Dunlap5-Jul-03 19:39

J. Dunlap

5-Jul-03 19:39

You also need to do:

newPanel.Size=[whatever-the-size-is];
this.Controls.Add(newPanel);

"Blessed are the peacemakers, for they shall be called sons of God." - Jesus

"You must be the change you wish to see in the world." - Mahatma Gandhi

frogb0x5-Jul-03 19:52

frogb0x

5-Jul-03 19:52

Still no love. This is my amended code:

private void btnCreate_Click(object sender, System.EventArgs e)
{
this.Hide();
UCCreate newPanel = new UCCreate();
newPanel.Location = new Point(376, 8);
newPanel.Size = new Size (280, 140);
this.Controls.Add(newPanel);
newPanel.Show();
}

James T. Johnson6-Jul-03 2:39

James T. Johnson

6-Jul-03 2:39

You're adding UCCreate to the control you are hiding, you need to add it to the controls collection of the form instead.

this.Parent.Controls.Add(newPanel); should give you what you want.

James

"I despise the city and much prefer being where a traffic jam means a line-up at McDonald's"
Me when telling a friend why I wouldn't want to live with him

Showing what folders exist

frogb0x6-Jul-03 17:16

frogb0x

6-Jul-03 17:16

So once I add that code into the constructor of my form, how does the first user control know about it? That is, how do I let other Controls know that newPanel exists?

Thanks for the tip! Smile | :)

eggie55-Jul-03 19:18

5-Jul-03 19:18

I have a folder called 'Shares' in my wwwroot. inside of that are about 12 or so folders with the names of a Husband & Wife in my family... e.g. "Ben.Anna", "Heidi.Scott", "Carylon.Roy" etc...

now, on my asp.net c# page I need the it to list the files in the "Shares" folder.... How would I do this?

/\ |_ E X E GG

James T. Johnson6-Jul-03 2:44

James T. Johnson

6-Jul-03 2:44

Use the System.IO.Directory.GetFiles and System.IO.Directory.GetDirectories methods, passing in the directory you want to retreive the files/directories from.

Use the Page objects MapPath method to go from the server's directory structure to one that can be used on a web page.

James

"I despise the city and much prefer being where a traffic jam means a line-up at McDonald's"
Me when telling a friend why I wouldn't want to live with him

eggie56-Jul-03 10:13

6-Jul-03 10:13

I'm pretty confused... could you code an example or something..?

just display the folders inside the folder "Shares" in a label...

example...

here's the folder Shares
and inside it are the folders: Ben.Anna, Alex.David, & Heidi.Scott

then on a aspx c# page you have a label...

now what is the code to make the label look like this...

Ben.Anna
Alex.David
Heidi.Scott

and have it update when ever a folder get's added to Shares or deleted from it...

please help.. i'm in a desperate rush... OMG | :OMG:

/\ |_ E X E GG

MrEyes7-Jul-03 6:38

MrEyes

7-Jul-03 6:38

The following code capable of doing what you need :

<br />
// using System.IO<br />
// make a reference to a directory<br />
DirectoryInfo di = new DirectoryInfo("c:\\");<br />
<br />
// get a reference to each directory in that directory<br />
DirectoryInfo[] diArr = di.GetDirectories();<br />
<br />
// print out the names of the directories<br />
foreach (DirectoryInfo dri in diArr)<br />
{<br />
  //this example outputs to the console, but you can use<br />
  //dri.Name to allocate values to labels etc etc<br />
  Console.WriteLine(dri.Name);<br />
}<br />

if this doesnt make any sense please feel free to ask

eggie57-Jul-03 10:54

7-Jul-03 10:54

this has to be a aspx webpage....

/\ |_ E X E GG

eggie57-Jul-03 11:05

7-Jul-03 11:05

Ok, I got it to work in aspx... i went...

labelPath.Text=dri.Name; // where "lablePath" is my label....

but anyways... when I run it, it only displays the last file in the folder, according to alpabetical order... so if there are 3 folders: Alex Ben & Carly.... only the highest letter will show up... Carly...

it does this in every folder.... what's wrong?

here's my full code...

private void Page_Load(object sender, System.EventArgs e)
{

    // using System.IO
    // make a reference to a directory
    DirectoryInfo di = new DirectoryInfo("C:\\program files\\");

    // get a reference to each directory in that directory
    DirectoryInfo[] diArr = di.GetDirectories();

    // print out the names of the directories
    foreach (DirectoryInfo dri in diArr)
    {
        //this example outputs to the console, but you can use
        //dri.Name to allocate values to labels etc etc
        labelPath.Text=dri.name;
    }

}