creating a custom exception

[hharry]

hello all,

quick syntax question. i am writing a custom exception class and came
across an example:

public class dataProvExcepti on : ApplicationExce ption
{
public dataProvExcepti on()
{
//
// TODO: Add constructor logic here
//
}

public dataProvExcepti on(string msg) : base(msg)
{
//
// TODO: Add constructor logic here
//

}

}

in the second constructor, what is the purpose of : base(msg) ?
i understand that the base keyword ids used to access members of the
base class ?

[Brian Gideon]

hharry wrote:

hello all,

quick syntax question. i am writing a custom exception class and came
across an example:

public class dataProvExcepti on : ApplicationExce ption
{
public dataProvExcepti on()
{
//
// TODO: Add constructor logic here
//
}

public dataProvExcepti on(string msg) : base(msg)
{
//
// TODO: Add constructor logic here
//

}

}

in the second constructor, what is the purpose of : base(msg) ?
i understand that the base keyword ids used to access members of the
base class ?

That calls a base class constructor. In this case you're passing the
exception message to a base class constructor that has one string
parameter.

Also, it is recommended to avoid the use of ApplicationExce ption. If I
remember correctly there was some discussion on whether or not to
deprecate it, but it doesn't appear that happened in 2.0. The idea was
that SystemException would be used for exceptions thrown by the CLR and
ApplicationExce ption would be used for non-CLR exceptions. The problem
is Microsoft didn't follow their own guideline so what seemed like a
good idea is nearly useless now.

http://blogs.msdn.com/kcwalina/archi...23/644822.aspx

Brian

[hharry]

thanks brian,

i'm testing this out now but if i've got this right:

if i initialize a new dataProvExcepti on object like this:
dataProvExcepti on myEx = new dataProvExcepti on("error text");

then, the constructor on the base class (ApplicationExc eption) will be
called instead of the constructor on the derived class
(dataProvExcept ion) ?

[Carl Daniel [VC++ MVP]]

hharry wrote:

thanks brian,

i'm testing this out now but if i've got this right:

if i initialize a new dataProvExcepti on object like this:
dataProvExcepti on myEx = new dataProvExcepti on("error text");

then, the constructor on the base class (ApplicationExc eption) will
be called instead of the constructor on the derived class
(dataProvExcept ion) ?

The constructor of the derived class _calls_ the constructor of the base
class. Both will run.

-cd