Basic OO question

[bz]

Hi,

I have a base class with several constructors and I want to create a
derived class, as below

class MyBase {
public MyBase() {...}
public MyBase(int ID) {...}
public MyBase(string ID_str) {...}
//....
public void Load() {....}
}

class MyDerived: MyBase {
public MyDerived() {....}
}

If I create a variable of type MyDerived, I can access Load method,
which obvious executes the Load from MyBase
However, I cannot create a variable of type MyDerived using other than
default constructor

MyDerived ob1 = new MyDerived(); // compiles ok
MyDerived ob2 = new MyDerived(SomeID);

This later gives me compilation error that there is no constructor
with 1 parameter.

So, the contructors from base class are not inherited, as with other
public methods? Do I have to define in MyDerived all constructors I
want to use, and they'll call the corresponding constructors from
MyBase?

Thanks

[Chris Mullins [MVP - C#]]

"bz" <bz*****@gmail.comwrote

So, the contructors from base class are not inherited, as with other
public methods?

Correct. Constructors are not inherited.

Do I have to define in MyDerived all constructors I
want to use, and they'll call the corresponding constructors
fromMyBase?

Yup. That's exactly what you need to do.

--
Chris Mullins

[Marc Gravell]

and they'll call the corresponding constructors from MyBase?

By default they will call the default (base) constuctor. To use
specific constructors, you need to give it more of a clue:

class ClassA {
public ClassA() {
Console.WriteLine("ClassA.ctor()");
}
public ClassA(int x) {
Console.WriteLine("ClassA.ctor(int x)");
}
}
class ClassB : ClassA {
public ClassB() { // uses ClassA.ctor() by default
Console.WriteLine("ClassB.ctor()");
}
public ClassB(int x) : base(x) { // need to be specific
Console.WriteLine("ClassB.ctor(int x)");
}
}

[=?Utf-8?B?QWRhbSBCaWVnYW5za2k=?=]

Hi bz,

Constructors are not inherited. However - a constructor in the deriving
class always has to (explicitly or implicitly) call base class's constructor.

More info here:
http://godevelop.blogspot.com/2007/1...tors-in-c.html
(that's my blog, I just coincidentally posted about what you're asking about
today!)
or here:
http://www.yoda.arachsys.com/csharp/constructors.html

Cheers,
--
_____________
Adam Bieganski
http://godevelop.blogspot.com
"bz" wrote:

Hi,

I have a base class with several constructors and I want to create a
derived class, as below

class MyBase {
public MyBase() {...}
public MyBase(int ID) {...}
public MyBase(string ID_str) {...}
//....
public void Load() {....}
}

class MyDerived: MyBase {
public MyDerived() {....}
}

If I create a variable of type MyDerived, I can access Load method,
which obvious executes the Load from MyBase
However, I cannot create a variable of type MyDerived using other than
default constructor

MyDerived ob1 = new MyDerived(); // compiles ok
MyDerived ob2 = new MyDerived(SomeID);

This later gives me compilation error that there is no constructor
with 1 parameter.

So, the contructors from base class are not inherited, as with other
public methods? Do I have to define in MyDerived all constructors I
want to use, and they'll call the corresponding constructors from
MyBase?

Thanks

[=?UTF-8?B?QXJuZSBWYWpow7hq?=]

bz wrote:

So, the contructors from base class are not inherited, as with other
public methods? Do I have to define in MyDerived all constructors I
want to use, and they'll call the corresponding constructors from
MyBase?

Yes.

Your IDE should have a "generate constructors from super class".

Note that:
should have != has

Arne

[bz]

Thank you all for your answers

Regards

On 8 Oct, 23:13, Arne Vajhøj <[e-mail]:

bz wrote:

So, the contructors from base class are not inherited, as with other
public methods? Do I have to define in MyDerived all constructors I
want to use, and they'll call the corresponding constructors from
MyBase?

Yes.

Your IDE should have a "generate constructors from super class".

Note that:
should have != has

Arne