Calling the base class constructor

[Jo Vermeulen]

Hello,

I was wondering how I could call the base class constructor from a derived
class constructor. In Java I could do something like

super(parameter);

I tried

base(parameter);

in C# but it doesn't compile. Any ideas?

Thanks in advance!

--
Jo Vermeulen
Student Computer Science at the tUL
email: [e-mail]
www: http://lumumba.luc.ac.be/jo

[Jon Skeet [C# MVP]]

Jo Vermeulen <[e-mail]> wrote:

I was wondering how I could call the base class constructor from a derived
class constructor. In Java I could do something like

super(parameter);

I tried

base(parameter);

in C# but it doesn't compile. Any ideas?

You do base (parameter) but in a different place:

public Derived() : base (...)
{
}

See http://www.pobox.com/~skeet/csharp/constructors.html for more
information.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Goran Genter]

Example :

public class BaseClass
{
public BaseClass(int i, int j)
{
...
}
}

public class DerivedClass : BaseClass
{
public DerivedClass(int i, int j, int k) : base(i, j) //this is
where you call base constructor
{
...
}
}

"Jo Vermeulen" <[e-mail]> wrote in message
news:pa****************************@lumumba.luc.ac .be...

Hello,

I was wondering how I could call the base class constructor from a derived
class constructor. In Java I could do something like

super(parameter);

I tried

base(parameter);

in C# but it doesn't compile. Any ideas?

Thanks in advance!

--
Jo Vermeulen
Student Computer Science at the tUL
email: [e-mail]
www: http://lumumba.luc.ac.be/jo

[Jo Vermeulen]

Op Tue, 25 May 2004 13:06:43 +0100, schreef Jon Skeet[ C# MVP]:

Jo Vermeulen <[e-mail]> wrote:
You do base (parameter) but in a different place:

public Derived() : base (...)
{
}

See http://www.pobox.com/~skeet/csharp/constructors.html for more
information.

Oh thanks, that's like C++ then.

Kind regards,

--
Jo Vermeulen
Student Computer Science at the tUL
email: [e-mail]
www: http://lumumba.luc.ac.be/jo

[cody]

> > I was wondering how I could call the base class constructor from a
derived

class constructor. In Java I could do something like

super(parameter);

I tried

base(parameter);

in C# but it doesn't compile. Any ideas?

You do base (parameter) but in a different place:

public Derived() : base (...)
{
}

See http://www.pobox.com/~skeet/csharp/constructors.html for more
information.

I've never understood why this special syntax is used here. Why not do it
like java and allow base(param);?
This would give you the freedom to do parameter processing before calling
the base ctor or you could do a try{}catch around the base()-call in future
versions of c#.

--
cody

Freeware Tools, Games and Humour
http://www.deutronium.de.vu || http://www.deutronium.tk

[Jon Skeet [C# MVP]]

cody <no****************@gmx.net> wrote:

See http://www.pobox.com/~skeet/csharp/constructors.html for more
information.

I've never understood why this special syntax is used here. Why not do it
like java and allow base(param);?
This would give you the freedom to do parameter processing before calling
the base ctor or you could do a try{}catch around the base()-call in future
versions of c#.

Just having the Java syntax wouldn't allow that - Java doesn't allow
anything else to happen before the constructor is called either.

For parameter processing, the normal approach is to write a static
method which massages the parameters appropriately, and use

public Foo(int x) : base (Massage(x))
{
....
}

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[cody]

> > I've never understood why this special syntax is used here. Why not do
it

like java and allow base(param);?
This would give you the freedom to do parameter processing before calling the base ctor or you could do a try{}catch around the base()-call in future versions of c#.
Just having the Java syntax wouldn't allow that - Java doesn't allow
anything else to happen before the constructor is called either.

I know, but this syntax would allow extensions for C# compilers in future to
do something like:

public GifFile(string s)
{
try
{
base (GetCurrentPath() + s + ".gif");
}
catch (IOException e)
{
base(); // call the empty ctor to create empty GIF which can be
filled dynamically
}
}

Theoretically this would bee possible, MSIL allows executing code before
ctor is called and call to multiple base ctors.
For parameter processing, the normal approach is to write a static
method which massages the parameters appropriately, and use

public Foo(int x) : base (Massage(x))
{
...
}

Good idea but it requires an additional method.

--
cody

[Freeware, Games and Humor]
www.deutronium.de.vu || www.deutronium.tk

[Jon Skeet [C# MVP]]

cody <pl*************************@gmx.de> wrote:

I know, but this syntax would allow extensions for C# compilers in future to
do something like:

public GifFile(string s)
{
try
{
base (GetCurrentPath() + s + ".gif");
}
catch (IOException e)
{
base(); // call the empty ctor to create empty GIF which can be
filled dynamically
}
}

Theoretically this would bee possible, MSIL allows executing code before
ctor is called and call to multiple base ctors.

It would allow for that syntax, yes - but whether they really want to
be encouraging that is a different matter.

For parameter processing, the normal approach is to write a static
method which massages the parameters appropriately, and use

public Foo(int x) : base (Massage(x))
{
...
}

Good idea but it requires an additional method.

Sure - I was just giving a workaround for the current restrictions in
some cases.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too