Re: how to pass variable between classes in window application - C# Discussion Boards

saud_a_k15-Jul-07 1:34

15-Jul-07 1:34

I have written an XML file using this code

private  void  AddBook(string  ISBN, string  title, string  author)
{

//
// Initialize booksElement if you are adding your first book.
//
if (booksElement == null)
{

booksElement = xmlDoc.CreateElement("Books");

}
 
//
// Same as tutorial; Adding and populating the elements
//
XmlElement bookElement = xmlDoc.CreateElement("Book");
 
XmlAttribute bookAttribute = xmlDoc.CreateAttribute("ISBN");
bookElement.SetAttributeNode(bookAttribute);
bookAttribute.Value = ISBN;
 
XmlElement titleElement = xmlDoc.CreateElement("title");
titleElement.InnerText = title;
bookElement.AppendChild(titleElement);
 
XmlElement authorElement = xmlDoc.CreateElement("author");
authorElement.InnerText = author;
bookElement.AppendChild(authorElement);
 
booksElement.AppendChild(bookElement);

xmlDoc.AppendChild(booksElement);
xmlDoc.Save(path);

}

it works fine for a new book, but I cannot OPEN an existing xml file and add a book (node) to it.
How do I append a node??

_____________________________________________________
Yea! I could be wrong...

Re: Append new node to XML file

mav.northwind15-Jul-07 2:18

mav.northwind

15-Jul-07 2:18

Hi!
You didn't show how you create the xmlDoc object, but XmlDocument has a Load() method you can use to open an existing xml file.
If you do open an existing file, you don't have to create the root entry (I guess it's booksElement, but can use xmlDoc.SelectSingleNode("/Books") to retrieve a reference to the existing node.

Regards,
mav

--
Black holes are the places where God divided by 0...

Re: Append new node to XML file

saud_a_k15-Jul-07 19:25

saud_a_k

15-Jul-07 19:25

I'm sorry I posted only the function of creating one node...
I grabbed code from www.kirupa.com , all of it is here..

private XmlDocument xmlDoc = new XmlDocument();
private XmlElement booksElement;
 
private void AddBook(string ISBN, string title, string author)
{

//
// Initialize booksElement if you are adding your first book.
//
if (booksElement == null)
{

booksElement = xmlDoc.CreateElement("Books");

}
 

XmlElement bookElement = xmlDoc.CreateElement("Book");
 
XmlAttribute bookAttribute = xmlDoc.CreateAttribute("ISBN");
bookElement.SetAttributeNode(bookAttribute);
bookAttribute.Value = ISBN;
 
XmlElement titleElement = xmlDoc.CreateElement("title");
titleElement.InnerText = title;
bookElement.AppendChild(titleElement);
 
XmlElement authorElement = xmlDoc.CreateElement("author");
authorElement.InnerText = author;
bookElement.AppendChild(authorElement);
 
booksElement.AppendChild(bookElement);

}
 
private void WriteToDisk(string path)
{

// Add the booksElement to our root element and write to disk
xmlDoc.AppendChild(booksElement);
xmlDoc.Save(path);

}
 
 
static void Main(string[] args)
{
 

Program bookList = new Program();
 
bookList.AddBook("0553212419", "Sherlock Holmes: Complete Novels and Stories, Vol 1", "Sir Arthur Conan Doyle");
bookList.AddBook("0743273567", "The Great Gatsby", "F. Scott Fitzgerald");
bookList.AddBook("0684826976", "Undaunted Courage", "Stephen E. Ambrose");
bookList.AddBook("0743203178", "Nothing Like It In the World", "Stephen E. Ambrose");
 
bookList.WriteToDisk(@"C:\books.xml");

}

So you see this creates a file OK.... But If I cannot ue this function to Append to the saved books.xml file.
meanwhile, I try the SelectSingleNode, and see if it works.

_____________________________________________________
Yea! I could be wrong...

how to pass variable between classes in window application

mhp13015-Jul-07 0:00

mhp130

15-Jul-07 0:00

Hi,there

I have a window application in C# (vs2003), I have one form class(Form1) and the Main[] located in the other class - MyProjectMain,

how do I pass variable between those two classes, for example I want to pass the arg[] that Main[] gets and populate in textBox1 of Form1?

Thanks a lot for your help,

namespace MyProject1
{
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.TextBox textBox1;
}
...

}

namespace MyProject1
{

public class MyprojectMain
{
[STAThread]
public static void Main(string[] args)
{
Application.Run(new Form1());
}
}

Re: how to pass variable between classes in window application

Guffa15-Jul-07 0:11

Guffa

15-Jul-07 0:11

Put a parameter in the constructor of the form:

public Form1(string[] args)

Pass the arguments when creating the form:

Application.Run(new Form1(args));

---
single minded; short sighted; long gone;

Re: how to pass variable between classes in window application

mhp13015-Jul-07 0:13

mhp130

15-Jul-07 0:13

Thanks,

but in general, how do I pass variables between classes in a window application? Do I always have to pass as arguments? or there are some namespace level variable I can use? I was a VB programmer so I've been spoiled that there are always application level variables to use.

Re: how to pass variable between classes in window application

Muhammad Gouda15-Jul-07 0:17

Muhammad Gouda

15-Jul-07 0:17

Just make it public
You can make it static to pass it through the class name
or you can create an instance from class2 into class1 to access non static members

Mohamed Gouda
Egypt

Re: how to pass variable between classes in window application

Colin Angus Mackay15-Jul-07 1:15

Colin Angus Mackay

15-Jul-07 1:15

Mohammed Gouda wrote:
Just make it public

Make what public? A field on the class. That is extremely bad practice: see Why make fields in a class private, why not just make them public?[^] and The public fields debate again[^]

Mohammed Gouda wrote:
You can make it static to pass it through the class name

And what happens when you have many instances of the same class? You pass the value to the static field and then you immediately affect all instances of the class rather than the one you are interested in.

Mohammed Gouda wrote:
you can create an instance from class2 into class1 to access non static members

I just don't understand where you are going with that.

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Re: how to pass variable between classes in window application

Muhammad Gouda15-Jul-07 1:30

Muhammad Gouda

15-Jul-07 1:30

Hey !!

Colin Angus Mackay wrote:
That is extremely bad practice

Thanks

One of your solutions is using properties (get and set)
Can you plz explain the difference between creating a Read/Write property for a private member AND making that member public?
I think making a Read/Write property is a redundant code (MAY BE I AM WRONG)
And when I diside to make a Read/Write property this means I will permit external Read/Write acces to the member (which can be achieved shortly be the keyword public)

Mohamed Gouda
Egypt

Re: how to pass variable between classes in window application

Luc Pattyn15-Jul-07 1:47

Luc Pattyn

15-Jul-07 1:47

Sure,

if you want to allow someone to set a text in one of your labels, you could:
1. provide a public property (or method) that does exactly that; this is good
2. make the label public, or provide a public property that gets a reference to the label,
so the caller itself can set the text. this is bad. Why ? because now the caller can
do many more things to your label, such as moving it around, changing its color, etc,
all things you did not intend to allow.

Hence: provide public properties/methods to do exactly what is needed, no more, no less.

Smile | :)

Luc Pattyn

try { [Search CP Articles] [Search CP Forums] [Forum Guidelines] [My Articles] }
catch { [Google] }

Re: how to pass variable between classes in window application

Colin Angus Mackay15-Jul-07 2:05

Colin Angus Mackay

15-Jul-07 2:05

Mohammed Gouda wrote:
Can you plz explain the difference between creating a Read/Write property for a private member AND making that member public?

Read the links I gave you.

Mohammed Gouda wrote:
And when I diside to make a Read/Write property this means I will permit external Read/Write acces to the member (which can be achieved shortly be the keyword public)

You are not granting read/write directly to the field, you are offering a way to access the field. If you read the links I gave you then you would already be aware of the advantages of that. In fact, there might not even be a field there at all. You are also giving your class the opportunity to veto any value that the outside class attempts to set on the field.

In short, there are vary few situations where making a field public is acceptable. Again, you would have seen that if you read the links I gave.

Re: how to pass variable between classes in window application

Colin Angus Mackay15-Jul-07 1:08

Colin Angus Mackay

15-Jul-07 1:08

mhp130 wrote:
but in general, how do I pass variables between classes in a window application?

Regardless of application type you can pass variables through constructor parameters, method parameters or properties.

mhp130 wrote:
or there are some namespace level variable I can use?

Good grief no! That is extremely bad practice.

mhp130 wrote:
I was a VB programmer so I've been spoiled that there are always application level variables to use.

That's not being spoiled, that's picking up bad habits... Which I suppose happens if you get spoiled also..

Windows Form in web form

ankit_mait14-Jul-07 23:03

ankit_mait

14-Jul-07 23:03

How to embedd a Windows form in a Webform

f

Re: Windows Form in web form

Manas Bhardwaj14-Jul-07 23:28

Manas Bhardwaj

14-Jul-07 23:28

ankit_mait wrote:
How to embedd a Windows form in a Webform

Can we?

FYI, you can not. By the way, if you post what exactly you wanna do, thn some can help you Rose | [Rose]

Re: Windows Form in web form

Christian Graus15-Jul-07 6:19

Christian Graus

15-Jul-07 6:19

Yeah you can. It's generally not a good idea, but you can.

Christian Graus - Microsoft MVP - C++

"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )

Re: Windows Form in web form

ankit_mait16-Jul-07 6:26

ankit_mait

16-Jul-07 6:26

I actually want to create an online Sudoku Solver so i thought i can create a windows application and then embedd it in an Webform...
This seems a little foolish but actually i have a 4 day time constraint and even if i cant create the webform i can atleast show an application to my professor

Re: Windows Form in web form

WillemM14-Jul-07 23:40

WillemM

14-Jul-07 23:40

It is possible, but I don't care to explain as it is very heavy to run on the server and you are probably better of building a true web application.

WM.

What about weapons of mass-construction?
"What? Its an Apple MacBook Pro. They are sexy!" - Paul Watson
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button appearance

Maddie from Dartford14-Jul-07 22:02

Maddie from Dartford

14-Jul-07 22:02

Hello,
I want to put a button on form which should give and appearance like "pressed" when clicked first time and it should come out on second click.

How can i implement this??
Thanks.

Gajesh

Re: button appearance

mav.northwind14-Jul-07 22:18

mav.northwind

14-Jul-07 22:18

There's a property for the CheckBox class that makes it appear like a button. In combination with setting Checked to true during startup that's exactly what you want.

Regards,
mav

--
Black holes are the places where God divided by 0...

Re: button appearance

Maddie from Dartford14-Jul-07 22:28

Maddie from Dartford

14-Jul-07 22:28