XML weird ??

[Vuong]

hi all

here my situation :

public class A
{
XmlDocument m_xmlDocument=null;
public A()
{
this.createEmptyXMLDocument();
// create an empty XMLdocument with XMLDeclaration and
// root Element into x_xmlDocument variable

}

// got a button ----
private void btn_new_click(object sender,System.EvenArgs e)
{
// add new employee
this.addEmployee(this.m_xmlDocument,strFirstname);
}
private addEmployee(XMLDocument doc,string firstname)
{
....... Do something to add new child into "doc" ;
}

}

What i got here is that, not just "doc" is added new child, "m_xmlDocument"
also is added new child , just the same as doc.
As far as i know, there's no way that can happen ....

Thanks,

[Truong Hong Thi]

> As far as i know, there's no way that can happen ....
Surely that happens. You pass a reference type as pamameter, then
modify its content. doc and m_xmlDocument reference the same memory
location, as the result, the child is inserted into m_xmlDocument. I
suggest you consult documentation about passing reference type as
parameter.

Thi - http://thith.blogspot.com

[Vuong]

How about this situation ??

public class A
{
int i=0;
public A()
{

}
private void btn_plus_click(object sender,System.EvenArgs e)
{
this.plus(i,2);
// i is still 0 here ;
}
public void plus(int a,int b)
{
a=a+b;
}
}

"Truong Hong Thi" <th*****@gmail.com> wrote in message
news:11**********************@g49g2000cwa.googlegr oups.com...

As far as i know, there's no way that can happen ....

Surely that happens. You pass a reference type as pamameter, then
modify its content. doc and m_xmlDocument reference the same memory
location, as the result, the child is inserted into m_xmlDocument. I
suggest you consult documentation about passing reference type as
parameter.

Thi - http://thith.blogspot.com

[Lenard Gunda]

Hi,

int (or System.Int32 what it really is) is a value type. Value types are
passed by value and not by reference.

You might want to read MSDN on value and reference types. For example,
there is an article about it in MSDN Magazine.

http://msdn.microsoft.com/msdnmag/issues/1200/dotnet/

Or check out other articles, you can find a lot with Google. For example:

http://www.knowdotnet.com/articles/referencetypes2.html
-Lenard

Vuong wrote:

How about this situation ??

public class A
{
int i=0;
public A()
{

}
private void btn_plus_click(object sender,System.EvenArgs e)
{
this.plus(i,2);
// i is still 0 here ;
}
public void plus(int a,int b)
{
a=a+b;
}
}

"Truong Hong Thi" <th*****@gmail.com> wrote in message
news:11**********************@g49g2000cwa.googlegr oups.com...

As far as i know, there's no way that can happen ....

Surely that happens. You pass a reference type as pamameter, then
modify its content. doc and m_xmlDocument reference the same memory
location, as the result, the child is inserted into m_xmlDocument. I
suggest you consult documentation about passing reference type as
parameter.

Thi - http://thith.blogspot.com

[Truong Hong Thi]

Yes, because int is of value type. XmlDocument is reference type. There
are many good articles on C# parameter passing. Do a search with your
favorite search engine.

[Vuong]

Yep
A very basic problem, a really big deal.

See ya

"Lenard Gunda" <ar***********@freemail.hu> wrote in message
news:Om**************@TK2MSFTNGP12.phx.gbl...

Hi,

int (or System.Int32 what it really is) is a value type. Value types are
passed by value and not by reference.

You might want to read MSDN on value and reference types. For example,
there is an article about it in MSDN Magazine.

http://msdn.microsoft.com/msdnmag/issues/1200/dotnet/

Or check out other articles, you can find a lot with Google. For example:

http://www.knowdotnet.com/articles/referencetypes2.html
-Lenard

Vuong wrote:

How about this situation ??

public class A
{
int i=0;
public A()
{

}
private void btn_plus_click(object sender,System.EvenArgs e)
{
this.plus(i,2);
// i is still 0 here ;
}
public void plus(int a,int b)
{
a=a+b;
}
}

"Truong Hong Thi" <th*****@gmail.com> wrote in message
news:11**********************@g49g2000cwa.googlegr oups.com...

As far as i know, there's no way that can happen ....

Surely that happens. You pass a reference type as pamameter, then
modify its content. doc and m_xmlDocument reference the same memory
location, as the result, the child is inserted into m_xmlDocument. I
suggest you consult documentation about passing reference type as
parameter.

Thi - http://thith.blogspot.com

[Vuong]

Yep
A very basic problem, a really big deal.

See ya

"Truong Hong Thi" <th*****@gmail.com> wrote in message
news:11*********************@o13g2000cwo.googlegro ups.com...

Yes, because int is of value type. XmlDocument is reference type. There
are many good articles on C# parameter passing. Do a search with your
favorite search engine.

[Jon Skeet [C# MVP]]

Lenard Gunda wrote:

int (or System.Int32 what it really is) is a value type. Value types are
passed by value and not by reference.

Whoa there - both reference type expressions and value type expressions
are passed by value by default. It's just that with reference type
expressions, the actual object is not passed at all - only a reference
is passed.

It's very important to maintain a distinction between passing a
reference by value and passing a value by reference.

See http://www.pobox.com/~skeet/csharp/parameters.html

Even if Int32 were a reference type, the "plus" method given wouldn't
change the passed value, because:

a = a+b;

would change the value of the (local) variable a, it wouldn't change
any data within the object which a originally referred to.

(Try it using strings instead of ints - string is a reference type.)

Jon

[Truong Hong Thi]

>Even if Int32 were a reference type, the "plus" method given wouldn't

change the passed value.

Ah, yes. I did not paid much attention to the snippet. Int32 is just as
immutable as string. It does not expose any methods allowing its
contents to be modified.