I'm trying to change the way a treeview works just a bit, i'm pretty new
to C# and now i'm running into overloading. I tried the following code
and it's yelling at me saying that no overload method takes 0 arguments.
#region tViewNodeCollec tion
public class tViewNodeCollec tion : TreeNodeCollect ion
{
private tView _owner;
private tViewNode _parent;
/// <summary>
/// Create a collection within a tViewItem
/// </summary>
/// <param name="parent"></param>
public tViewNodeCollec tion(tViewNode parent)
{
_parent = parent;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner)
{
_owner = owner;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner, tViewNode parent)
{
_owner = owner;
_parent = parent;
}
}
#endregion
so then I tried a series of different :this(something ) but that started
scaring me since I really don't understand overloading - Could someone
shed some light on this for me? 10  2679 
An overloaded method is a method that differs from all methods of the same
name in so far as it has a different number or types of its arguments. A
different return type does not constitute an overload. If you get an error
stating that no overload has 0 arguments then you are calling a method with
no arguments and you have no overloaded method that takes zero arguments.
Either instantiate the class with a constructor call with arguments or
provide an explicit constructor with zero arguments. In C# if you provide an
overloaded constructor you no longer get a default constructor (zero
arguments) and need to provide one. I think this is your problem.
Thomas P. Skinner [MVP]
"Benny Raymond" <be***@pocketro cks.com> wrote in message
news:%2******** ********@tk2msf tngp13.phx.gbl. .. I'm trying to change the way a treeview works just a bit, i'm pretty new
to C# and now i'm running into overloading. I tried the following code
and it's yelling at me saying that no overload method takes 0 arguments.
#region tViewNodeCollec tion
public class tViewNodeCollec tion : TreeNodeCollect ion
{
private tView _owner;
private tViewNode _parent;
/// <summary>
/// Create a collection within a tViewItem
/// </summary>
/// <param name="parent"></param>
public tViewNodeCollec tion(tViewNode parent)
{
_parent = parent;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner)
{
_owner = owner;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner, tViewNode parent)
{
_owner = owner;
_parent = parent;
}
}
#endregion
so then I tried a series of different :this(something ) but that started
scaring me since I really don't understand overloading - Could someone
shed some light on this for me?
I believe that the constructor of the TreeViewCollect ion has been set to
private so effectively it can't be inherited.
The error message is a bit misleading though (it suggests that there is a
public constructor that does not have zero args - and hence in that case you
would be able to call it from your derived class) .
see for instance... http://www.groupsrv.com/dotnet/viewtopic.php?t=16350
Hope this helps
Br,
Mark.
P.S.
Benny, although this is really something that is open to your/ your company
preference, when naming types you should (IMHO) not prefix them with
"t" -that is really a Delphi thing (but if it works for you then please
ignore my advice).
P.P.S.
You mention that you do not understand overloading, well in essence creating
an overload means that you are adding an additional function call to a class
which has the same name that is distinguished by it's type signature.
For instance
public void SayHello()
{SayHello();} //just calling overload method to save code in class
public void SayHello(string name)
{ string display = "Hello";
if name.Length > 0
display += name;
Console.WriteLi ne(display);
}
Which will mean that the Class would provide two method calls..
1 that allows you to SayHello without any arguments and the other to allow
you to SayHello with a string argument.
***I think you are also getting a little bit confused with overloading and
overriding - they are two DIFFERENT concepts. You should ideally read up on
both since they are crucial to good OOP***
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uK******** ******@TK2MSFTN GP15.phx.gbl... An overloaded method is a method that differs from all methods of the same
name in so far as it has a different number or types of its arguments. A
different return type does not constitute an overload. If you get an error
stating that no overload has 0 arguments then you are calling a method
with no arguments and you have no overloaded method that takes zero
arguments. Either instantiate the class with a constructor call with
arguments or provide an explicit constructor with zero arguments. In C# if
you provide an overloaded constructor you no longer get a default
constructor (zero arguments) and need to provide one. I think this is your
problem.
Thomas P. Skinner [MVP]
"Benny Raymond" <be***@pocketro cks.com> wrote in message
news:%2******** ********@tk2msf tngp13.phx.gbl. .. I'm trying to change the way a treeview works just a bit, i'm pretty new
to C# and now i'm running into overloading. I tried the following code
and it's yelling at me saying that no overload method takes 0 arguments.
#region tViewNodeCollec tion
public class tViewNodeCollec tion : TreeNodeCollect ion
{
private tView _owner;
private tViewNode _parent;
/// <summary>
/// Create a collection within a tViewItem
/// </summary>
/// <param name="parent"></param>
public tViewNodeCollec tion(tViewNode parent)
{
_parent = parent;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner)
{
_owner = owner;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner, tViewNode parent)
{
_owner = owner;
_parent = parent;
}
}
#endregion
so then I tried a series of different :this(something ) but that started
scaring me since I really don't understand overloading - Could someone
shed some light on this for me?
A private constructor with zero args doesn't prevent inheritance from that
class. Basically the private constructor with zero args is normally used to
force the programming to instantiate the class with an overloaded
constructor. The derived class would need to explicitly invoke the
overloaded constructor in the base class.
The TreeNodeCollect ion does seem a bit strange in that no constructors are
documented. That would mean the class must be constructed via a public
static method. However I can't find one documented. It appears that the
TreeNodeCollect ion gets instantiated by the TreeView class by some subtle
method. In this case I agree that one can't inherit from TreeNodeCollect ion.
BTW, TreeNodeCollect ion is NOT documented as sealed. The result is the same
I guess. Interesting.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:eK******** ******@TK2MSFTN GP14.phx.gbl... I believe that the constructor of the TreeViewCollect ion has been set to
private so effectively it can't be inherited.
The error message is a bit misleading though (it suggests that there is a
public constructor that does not have zero args - and hence in that case
you would be able to call it from your derived class) .
see for instance...
http://www.groupsrv.com/dotnet/viewtopic.php?t=16350
Hope this helps
Br,
Mark.
P.S.
Benny, although this is really something that is open to your/ your
company preference, when naming types you should (IMHO) not prefix them
with "t" -that is really a Delphi thing (but if it works for you then
please ignore my advice).
P.P.S.
You mention that you do not understand overloading, well in essence
creating an overload means that you are adding an additional function call
to a class which has the same name that is distinguished by it's type
signature.
For instance
public void SayHello()
{SayHello();} //just calling overload method to save code in class
public void SayHello(string name)
{ string display = "Hello";
if name.Length > 0
display += name;
Console.WriteLi ne(display);
}
Which will mean that the Class would provide two method calls..
1 that allows you to SayHello without any arguments and the other to allow
you to SayHello with a string argument.
***I think you are also getting a little bit confused with overloading and
overriding - they are two DIFFERENT concepts. You should ideally read up
on both since they are crucial to good OOP***
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uK******** ******@TK2MSFTN GP15.phx.gbl... An overloaded method is a method that differs from all methods of the
same name in so far as it has a different number or types of its
arguments. A different return type does not constitute an overload. If
you get an error stating that no overload has 0 arguments then you are
calling a method with no arguments and you have no overloaded method that
takes zero arguments. Either instantiate the class with a constructor
call with arguments or provide an explicit constructor with zero
arguments. In C# if you provide an overloaded constructor you no longer
get a default constructor (zero arguments) and need to provide one. I
think this is your problem.
Thomas P. Skinner [MVP]
"Benny Raymond" <be***@pocketro cks.com> wrote in message
news:%2******** ********@tk2msf tngp13.phx.gbl. .. I'm trying to change the way a treeview works just a bit, i'm pretty new
to C# and now i'm running into overloading. I tried the following code
and it's yelling at me saying that no overload method takes 0 arguments.
#region tViewNodeCollec tion
public class tViewNodeCollec tion : TreeNodeCollect ion
{
private tView _owner;
private tViewNode _parent;
/// <summary>
/// Create a collection within a tViewItem
/// </summary>
/// <param name="parent"></param>
public tViewNodeCollec tion(tViewNode parent)
{
_parent = parent;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner)
{
_owner = owner;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner, tViewNode parent)
{
_owner = owner;
_parent = parent;
}
}
#endregion
so then I tried a series of different :this(something ) but that started
scaring me since I really don't understand overloading - Could someone
shed some light on this for me?
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in
news:uF******** ******@TK2MSFTN GP15.phx.gbl: A private constructor with zero args doesn't prevent inheritance
from that class. Basically the private constructor with zero
args is normally used to force the programming to instantiate
the class with an overloaded constructor. The derived class
would need to explicitly invoke the overloaded constructor in
the base class.
The TreeNodeCollect ion does seem a bit strange in that no
constructors are documented. That would mean the class must be
constructed via a public static method. However I can't find one
documented. It appears that the TreeNodeCollect ion gets
instantiated by the TreeView class by some subtle method. In
this case I agree that one can't inherit from
TreeNodeCollect ion. BTW, TreeNodeCollect ion is NOT documented as
sealed. The result is the same I guess. Interesting.
Thomas,
Using Lutz Roeder's Reflector utility, it appears that
TreeNodeCollect ion's only constructor is scoped as internal. The
types w/i System.Windows. Forms.dll can use it like any other type,
but us poor serfs on the "outside" can't construct our own instances
of TreeNodeCollect ion :-(.
Chris.
-------------
C.R. Timmons Consulting, Inc. http://www.crtimmonsinc.com/
Chris,
Now why didn't I think of that? This makes complete sense. I was thinking
maybe an undocumented static method or something, but internal is so much
simpler. Thanks for this info.
Thomas P. Skinner [MVP]
"Chris R. Timmons" <crtimmons@X_NO SPAM_Xcrtimmons inc.com> wrote in message
news:Xn******** *************** ***********@207 .46.248.16... "Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in
news:uF******** ******@TK2MSFTN GP15.phx.gbl:
A private constructor with zero args doesn't prevent inheritance
from that class. Basically the private constructor with zero
args is normally used to force the programming to instantiate
the class with an overloaded constructor. The derived class
would need to explicitly invoke the overloaded constructor in
the base class.
The TreeNodeCollect ion does seem a bit strange in that no
constructors are documented. That would mean the class must be
constructed via a public static method. However I can't find one
documented. It appears that the TreeNodeCollect ion gets
instantiated by the TreeView class by some subtle method. In
this case I agree that one can't inherit from
TreeNodeCollect ion. BTW, TreeNodeCollect ion is NOT documented as
sealed. The result is the same I guess. Interesting.
Thomas,
Using Lutz Roeder's Reflector utility, it appears that
TreeNodeCollect ion's only constructor is scoped as internal. The
types w/i System.Windows. Forms.dll can use it like any other type,
but us poor serfs on the "outside" can't construct our own instances
of TreeNodeCollect ion :-(.
Chris.
-------------
C.R. Timmons Consulting, Inc.
http://www.crtimmonsinc.com/
Hi Thomas please see replies....
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uF******** ******@TK2MSFTN GP15.phx.gbl... A private constructor with zero args doesn't prevent inheritance from that
class. Basically the private constructor with zero args is normally used to
force the programming to instantiate the class with an overloaded
constructor. The derived class would need to explicitly invoke the
overloaded constructor in the base class.
Incorrect - A private constructor *will* prevent inheritance *if* it is
the only constructor available in the class (which I suggested in the
original post). Your statement is correct only *if* there is an available
constructor visible to the code outside the class (public) or to the
inheriting class (protected - if both classes in same assembly). One reason
you might want to do this is to enforce strict object creation through an
object factory method. For instance the following class cannot be
inherited...
public class Parent
{
string name;
private Parent(string s) //only constructor: is private and prevents
inheritance since any inheriting classes cannot see the base constructor
{
name = s;
}
public static Parent CreateParent(st ring s)
{
if (s == null || s.Length == 0)
{
throw new Exception("Inva lid string specified when building new
object");
}
return new Parent(s);
}
}
You are obviously correct is stating another reason why a private default
constructor is used -to enforce construction through an overloaded
constructor *although* this is strictly not necessary since a default
constructor is only used if :-
i. No constructor is specified in a class
ii. If the default constructor has been explicitly declared - which is the
default behaviour of Visual Studio code generator.
For instance the following code can only be created using the constructor
with a string params...
public class Class2
{
//the lack of default constructor effectively means that the class can
only
//be instanciated using the constructor with a string parameter.
public Class2(string s)
{
}
}
The TreeNodeCollect ion does seem a bit strange in that no constructors are
documented. That would mean the class must be constructed via a public
static method. However I can't find one documented. It appears that the
TreeNodeCollect ion gets instantiated by the TreeView class by some subtle
method. In this case I agree that one can't inherit from
TreeNodeCollect ion. BTW, TreeNodeCollect ion is NOT documented as sealed.
The result is the same I guess. Interesting.
Thankfully Chris has got to the bottom of this one. Interesting subject
this. Like you I noticed the lack of constructor documentation for this
class. I really wish Microsoft would document exactly the internals of the
class libraries -but I guess you cant have everything.
Best Regards,
Mark Broadbent.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:eK******** ******@TK2MSFTN GP14.phx.gbl...I believe that the constructor of the TreeViewCollect ion has been set to
private so effectively it can't be inherited.
The error message is a bit misleading though (it suggests that there is a
public constructor that does not have zero args - and hence in that case
you would be able to call it from your derived class) .
see for instance...
http://www.groupsrv.com/dotnet/viewtopic.php?t=16350
Hope this helps
Br,
Mark.
P.S.
Benny, although this is really something that is open to your/ your
company preference, when naming types you should (IMHO) not prefix them
with "t" -that is really a Delphi thing (but if it works for you then
please ignore my advice).
P.P.S.
You mention that you do not understand overloading, well in essence
creating an overload means that you are adding an additional function
call to a class which has the same name that is distinguished by it's
type signature.
For instance
public void SayHello()
{SayHello();} //just calling overload method to save code in class
public void SayHello(string name)
{ string display = "Hello";
if name.Length > 0
display += name;
Console.WriteLi ne(display);
}
Which will mean that the Class would provide two method calls..
1 that allows you to SayHello without any arguments and the other to
allow you to SayHello with a string argument.
***I think you are also getting a little bit confused with overloading
and overriding - they are two DIFFERENT concepts. You should ideally read
up on both since they are crucial to good OOP***
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uK******** ******@TK2MSFTN GP15.phx.gbl... An overloaded method is a method that differs from all methods of the
same name in so far as it has a different number or types of its
arguments. A different return type does not constitute an overload. If
you get an error stating that no overload has 0 arguments then you are
calling a method with no arguments and you have no overloaded method
that takes zero arguments. Either instantiate the class with a
constructor call with arguments or provide an explicit constructor with
zero arguments. In C# if you provide an overloaded constructor you no
longer get a default constructor (zero arguments) and need to provide
one. I think this is your problem.
Thomas P. Skinner [MVP]
"Benny Raymond" <be***@pocketro cks.com> wrote in message
news:%2******** ********@tk2msf tngp13.phx.gbl. ..
I'm trying to change the way a treeview works just a bit, i'm pretty
new to C# and now i'm running into overloading. I tried the following
code and it's yelling at me saying that no overload method takes 0
arguments.
#region tViewNodeCollec tion
public class tViewNodeCollec tion : TreeNodeCollect ion
{
private tView _owner;
private tViewNode _parent;
/// <summary>
/// Create a collection within a tViewItem
/// </summary>
/// <param name="parent"></param>
public tViewNodeCollec tion(tViewNode parent)
{
_parent = parent;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner)
{
_owner = owner;
}
/// <summary>
/// Create a new instance of tViewNodeCollec tion
/// </summary>
/// <param name="owner"></param>
public tViewNodeCollec tion(tView owner, tViewNode parent)
{
_owner = owner;
_parent = parent;
}
}
#endregion
so then I tried a series of different :this(something ) but that started
scaring me since I really don't understand overloading - Could someone
shed some light on this for me?
Yes, but that's not what I said. Read it again at bit more carefully before
criticizing.. I was responding to a conjecture that a private default
constructor always prevents inheritance. It doesn't if there are public
overloaded constructors as you well point out. I never said a class with
ONLY a private default constructor can be inherited.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:Or******** *****@TK2MSFTNG P11.phx.gbl... Hi Thomas please see replies....
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uF******** ******@TK2MSFTN GP15.phx.gbl...A private constructor with zero args doesn't prevent inheritance from that
class. Basically the private constructor with zero args is normally used
to force the programming to instantiate the class with an overloaded
constructor . The derived class would need to explicitly invoke the
overloaded constructor in the base class.
Incorrect - A private constructor *will* prevent inheritance *if* it is
the only constructor available in the class (which I suggested in the
original post). Your statement is correct only *if* there is an available
constructor visible to the code outside the class (public) or to the
inheriting class (protected - if both classes in same assembly). One
reason you might want to do this is to enforce strict object creation
through an object factory method. For instance the following class cannot
be inherited...
public class Parent
{
string name;
private Parent(string s) //only constructor: is private and prevents
inheritance since any inheriting classes cannot see the base constructor
{
name = s;
}
public static Parent CreateParent(st ring s)
{
if (s == null || s.Length == 0)
{
throw new Exception("Inva lid string specified when building new
object");
}
return new Parent(s);
}
}
You are obviously correct is stating another reason why a private default
constructor is used -to enforce construction through an overloaded
constructor *although* this is strictly not necessary since a default
constructor is only used if :-
i. No constructor is specified in a class
ii. If the default constructor has been explicitly declared - which is the
default behaviour of Visual Studio code generator.
For instance the following code can only be created using the constructor
with a string params...
public class Class2
{
//the lack of default constructor effectively means that the class can
only
//be instanciated using the constructor with a string parameter.
public Class2(string s)
{
}
}
The TreeNodeCollect ion does seem a bit strange in that no constructors
are documented. That would mean the class must be constructed via a
public static method. However I can't find one documented. It appears
that the TreeNodeCollect ion gets instantiated by the TreeView class by
some subtle method. In this case I agree that one can't inherit from
TreeNodeCollect ion. BTW, TreeNodeCollect ion is NOT documented as sealed.
The result is the same I guess. Interesting.
Thankfully Chris has got to the bottom of this one. Interesting subject
this. Like you I noticed the lack of constructor documentation for this
class. I really wish Microsoft would document exactly the internals of the
class libraries -but I guess you cant have everything.
Best Regards,
Mark Broadbent.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:eK******** ******@TK2MSFTN GP14.phx.gbl...I believe that the constructor of the TreeViewCollect ion has been set to
private so effectively it can't be inherited.
The error message is a bit misleading though (it suggests that there is
a public constructor that does not have zero args - and hence in that
case you would be able to call it from your derived class) .
see for instance...
http://www.groupsrv.com/dotnet/viewtopic.php?t=16350
Hope this helps
Br,
Mark.
P.S.
Benny, although this is really something that is open to your/ your
company preference, when naming types you should (IMHO) not prefix them
with "t" -that is really a Delphi thing (but if it works for you then
please ignore my advice).
P.P.S.
You mention that you do not understand overloading, well in essence
creating an overload means that you are adding an additional function
call to a class which has the same name that is distinguished by it's
type signature.
For instance
public void SayHello()
{SayHello();} //just calling overload method to save code in class
public void SayHello(string name)
{ string display = "Hello";
if name.Length > 0
display += name;
Console.WriteLi ne(display);
}
Which will mean that the Class would provide two method calls..
1 that allows you to SayHello without any arguments and the other to
allow you to SayHello with a string argument.
***I think you are also getting a little bit confused with overloading
and overriding - they are two DIFFERENT concepts. You should ideally
read up on both since they are crucial to good OOP***
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uK******** ******@TK2MSFTN GP15.phx.gbl...
An overloaded method is a method that differs from all methods of the
same name in so far as it has a different number or types of its
arguments. A different return type does not constitute an overload. If
you get an error stating that no overload has 0 arguments then you are
calling a method with no arguments and you have no overloaded method
that takes zero arguments. Either instantiate the class with a
constructor call with arguments or provide an explicit constructor with
zero arguments. In C# if you provide an overloaded constructor you no
longer get a default constructor (zero arguments) and need to provide
one. I think this is your problem.
Thomas P. Skinner [MVP]
"Benny Raymond" <be***@pocketro cks.com> wrote in message
news:%2******** ********@tk2msf tngp13.phx.gbl. ..
> I'm trying to change the way a treeview works just a bit, i'm pretty
> new to C# and now i'm running into overloading. I tried the
> following code and it's yelling at me saying that no overload method
> takes 0 arguments.
>
> #region tViewNodeCollec tion
> public class tViewNodeCollec tion : TreeNodeCollect ion
> {
> private tView _owner;
> private tViewNode _parent;
> /// <summary>
> /// Create a collection within a tViewItem
> /// </summary>
> /// <param name="parent"></param>
> public tViewNodeCollec tion(tViewNode parent)
> {
> _parent = parent;
> }
> /// <summary>
> /// Create a new instance of tViewNodeCollec tion
> /// </summary>
> /// <param name="owner"></param>
> public tViewNodeCollec tion(tView owner)
> {
> _owner = owner;
> }
> /// <summary>
> /// Create a new instance of tViewNodeCollec tion
> /// </summary>
> /// <param name="owner"></param>
> public tViewNodeCollec tion(tView owner, tViewNode parent)
> {
> _owner = owner;
> _parent = parent;
> }
> }
> #endregion
>
>
> so then I tried a series of different :this(something ) but that
> started scaring me since I really don't understand overloading - Could
> someone shed some light on this for me?
1. I think you will find that you did implicitly say exactly that ...."A
private constructor with zero args doesn't prevent inheritance from that
class"
-since you were attempting to correct my original statement -which by the
way mentions NOTHING about overloaded constructor in the base class and in
addition nowhere in my statement do I say ALWAYS prevents -just in that one
instance.
2. I was not critizing, I was correcting (or for the sake of
Benny...clarify ing your misleading statement). So before you start flaming
me please think about what you are saying and take time to read the posts
properly.
3. Your MVP doesnot entitle you to be correct on every occasion so get over
it and move on!
NUFF SAID!
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:%2******** ********@TK2MSF TNGP09.phx.gbl. .. Yes, but that's not what I said. Read it again at bit more carefully
before criticizing.. I was responding to a conjecture that a private
default constructor always prevents inheritance. It doesn't if there are
public overloaded constructors as you well point out. I never said a class
with ONLY a private default constructor can be inherited.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:Or******** *****@TK2MSFTNG P11.phx.gbl... Hi Thomas please see replies....
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uF******** ******@TK2MSFTN GP15.phx.gbl...A private constructor with zero args doesn't prevent inheritance from
that class. Basically the private constructor with zero args is normally
used to force the programming to instantiate the class with an overloaded
constructo r. The derived class would need to explicitly invoke the
overloaded constructor in the base class.
Incorrect - A private constructor *will* prevent inheritance *if* it
is the only constructor available in the class (which I suggested in the
original post). Your statement is correct only *if* there is an available
constructor visible to the code outside the class (public) or to the
inheriting class (protected - if both classes in same assembly). One
reason you might want to do this is to enforce strict object creation
through an object factory method. For instance the following class cannot
be inherited...
public class Parent
{
string name;
private Parent(string s) //only constructor: is private and prevents
inheritance since any inheriting classes cannot see the base constructor
{
name = s;
}
public static Parent CreateParent(st ring s)
{
if (s == null || s.Length == 0)
{
throw new Exception("Inva lid string specified when building new
object");
}
return new Parent(s);
}
}
You are obviously correct is stating another reason why a private default
constructor is used -to enforce construction through an overloaded
constructor *although* this is strictly not necessary since a default
constructor is only used if :-
i. No constructor is specified in a class
ii. If the default constructor has been explicitly declared - which is
the default behaviour of Visual Studio code generator.
For instance the following code can only be created using the constructor
with a string params...
public class Class2
{
//the lack of default constructor effectively means that the class can
only
//be instanciated using the constructor with a string parameter.
public Class2(string s)
{
}
}
The TreeNodeCollect ion does seem a bit strange in that no constructors
are documented. That would mean the class must be constructed via a
public static method. However I can't find one documented. It appears
that the TreeNodeCollect ion gets instantiated by the TreeView class by
some subtle method. In this case I agree that one can't inherit from
TreeNodeCollect ion. BTW, TreeNodeCollect ion is NOT documented as sealed.
The result is the same I guess. Interesting.
Thankfully Chris has got to the bottom of this one. Interesting subject
this. Like you I noticed the lack of constructor documentation for this
class. I really wish Microsoft would document exactly the internals of
the class libraries -but I guess you cant have everything.
Best Regards,
Mark Broadbent.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:eK******** ******@TK2MSFTN GP14.phx.gbl...
I believe that the constructor of the TreeViewCollect ion has been set to
private so effectively it can't be inherited.
The error message is a bit misleading though (it suggests that there is
a public constructor that does not have zero args - and hence in that
case you would be able to call it from your derived class) .
see for instance...
http://www.groupsrv.com/dotnet/viewtopic.php?t=16350
Hope this helps
Br,
Mark.
P.S.
Benny, although this is really something that is open to your/ your
company preference, when naming types you should (IMHO) not prefix them
with "t" -that is really a Delphi thing (but if it works for you then
please ignore my advice).
P.P.S.
You mention that you do not understand overloading, well in essence
creating an overload means that you are adding an additional function
call to a class which has the same name that is distinguished by it's
type signature.
For instance
public void SayHello()
{SayHello();} //just calling overload method to save code in
class
public void SayHello(string name)
{ string display = "Hello";
if name.Length > 0
display += name;
Console.WriteLi ne(display);
}
Which will mean that the Class would provide two method calls..
1 that allows you to SayHello without any arguments and the other to
allow you to SayHello with a string argument.
***I think you are also getting a little bit confused with overloading
and overriding - they are two DIFFERENT concepts. You should ideally
read up on both since they are crucial to good OOP***
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uK******** ******@TK2MSFTN GP15.phx.gbl...
> An overloaded method is a method that differs from all methods of the
> same name in so far as it has a different number or types of its
> arguments. A different return type does not constitute an overload. If
> you get an error stating that no overload has 0 arguments then you are
> calling a method with no arguments and you have no overloaded method
> that takes zero arguments. Either instantiate the class with a
> constructor call with arguments or provide an explicit constructor
> with zero arguments. In C# if you provide an overloaded constructor
> you no longer get a default constructor (zero arguments) and need to
> provide one. I think this is your problem.
>
> Thomas P. Skinner [MVP]
>
> "Benny Raymond" <be***@pocketro cks.com> wrote in message
> news:%2******** ********@tk2msf tngp13.phx.gbl. ..
>> I'm trying to change the way a treeview works just a bit, i'm pretty
>> new to C# and now i'm running into overloading. I tried the
>> following code and it's yelling at me saying that no overload method
>> takes 0 arguments.
>>
>> #region tViewNodeCollec tion
>> public class tViewNodeCollec tion : TreeNodeCollect ion
>> {
>> private tView _owner;
>> private tViewNode _parent;
>> /// <summary>
>> /// Create a collection within a tViewItem
>> /// </summary>
>> /// <param name="parent"></param>
>> public tViewNodeCollec tion(tViewNode parent)
>> {
>> _parent = parent;
>> }
>> /// <summary>
>> /// Create a new instance of tViewNodeCollec tion
>> /// </summary>
>> /// <param name="owner"></param>
>> public tViewNodeCollec tion(tView owner)
>> {
>> _owner = owner;
>> }
>> /// <summary>
>> /// Create a new instance of tViewNodeCollec tion
>> /// </summary>
>> /// <param name="owner"></param>
>> public tViewNodeCollec tion(tView owner, tViewNode parent)
>> {
>> _owner = owner;
>> _parent = parent;
>> }
>> }
>> #endregion
>>
>>
>> so then I tried a series of different :this(something ) but that
>> started scaring me since I really don't understand overloading -
>> Could someone shed some light on this for me?
>
>
Mark,
I apologize if I interpreted your original statement incorrectly. However I
believe the implication was that a private default constructor always
prevents inheritance even if you did not mention overloaded constructors or
the word always. My mistake. I think you were also a bit quick to jump on my
most recent statement. Nothing I said was incorrect as stated. I only made a
mistake on what I said because you misinterpreted it.
I will ignore comment 3 and get on with things.
Thomas P. Skinner [MVP]
Mark Broadbent" <no****@nospam. com> wrote in message
news:e1******** ******@tk2msftn gp13.phx.gbl... 1. I think you will find that you did implicitly say exactly that ...."A
private constructor with zero args doesn't prevent inheritance from that
class"
-since you were attempting to correct my original statement -which by the
way mentions NOTHING about overloaded constructor in the base class and in
addition nowhere in my statement do I say ALWAYS prevents -just in that
one instance.
2. I was not critizing, I was correcting (or for the sake of
Benny...clarify ing your misleading statement). So before you start flaming
me please think about what you are saying and take time to read the posts
properly.
3. Your MVP doesnot entitle you to be correct on every occasion so get
over it and move on!
NUFF SAID!
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:%2******** ********@TK2MSF TNGP09.phx.gbl. .. Yes, but that's not what I said. Read it again at bit more carefully
before criticizing.. I was responding to a conjecture that a private
default constructor always prevents inheritance. It doesn't if there are
public overloaded constructors as you well point out. I never said a
class with ONLY a private default constructor can be inherited.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:Or******** *****@TK2MSFTNG P11.phx.gbl... Hi Thomas please see replies....
"Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
news:uF******** ******@TK2MSFTN GP15.phx.gbl...
A private constructor with zero args doesn't prevent inheritance from
that class. Basically the private constructor with zero args is normally
used to force the programming to instantiate the class with an
overloade d constructor. The derived class would need to explicitly
invoke the overloaded constructor in the base class.
Incorrect - A private constructor *will* prevent inheritance *if* it
is the only constructor available in the class (which I suggested in the
original post). Your statement is correct only *if* there is an
available constructor visible to the code outside the class (public) or
to the inheriting class (protected - if both classes in same assembly).
One reason you might want to do this is to enforce strict object
creation through an object factory method. For instance the following
class cannot be inherited...
public class Parent
{
string name;
private Parent(string s) //only constructor: is private and prevents
inheritance since any inheriting classes cannot see the base constructor
{
name = s;
}
public static Parent CreateParent(st ring s)
{
if (s == null || s.Length == 0)
{
throw new Exception("Inva lid string specified when building new
object");
}
return new Parent(s);
}
}
You are obviously correct is stating another reason why a private
default constructor is used -to enforce construction through an
overloaded constructor *although* this is strictly not necessary since a
default constructor is only used if :-
i. No constructor is specified in a class
ii. If the default constructor has been explicitly declared - which is
the default behaviour of Visual Studio code generator.
For instance the following code can only be created using the
constructor with a string params...
public class Class2
{
//the lack of default constructor effectively means that the class can
only
//be instanciated using the constructor with a string parameter.
public Class2(string s)
{
}
}
The TreeNodeCollect ion does seem a bit strange in that no constructors
are documented. That would mean the class must be constructed via a
public static method. However I can't find one documented. It appears
that the TreeNodeCollect ion gets instantiated by the TreeView class by
some subtle method. In this case I agree that one can't inherit from
TreeNodeCollect ion. BTW, TreeNodeCollect ion is NOT documented as
sealed. The result is the same I guess. Interesting.
Thankfully Chris has got to the bottom of this one. Interesting subject
this. Like you I noticed the lack of constructor documentation for this
class. I really wish Microsoft would document exactly the internals of
the class libraries -but I guess you cant have everything.
Best Regards,
Mark Broadbent.
Thomas P. Skinner [MVP]
"Mark Broadbent" <no****@nospam. com> wrote in message
news:eK******** ******@TK2MSFTN GP14.phx.gbl...
>I believe that the constructor of the TreeViewCollect ion has been set
>to private so effectively it can't be inherited.
> The error message is a bit misleading though (it suggests that there
> is a public constructor that does not have zero args - and hence in
> that case you would be able to call it from your derived class) .
>
> see for instance...
> http://www.groupsrv.com/dotnet/viewtopic.php?t=16350
>
> Hope this helps
>
> Br,
>
> Mark.
>
> P.S.
> Benny, although this is really something that is open to your/ your
> company preference, when naming types you should (IMHO) not prefix
> them with "t" -that is really a Delphi thing (but if it works for you
> then please ignore my advice).
>
> P.P.S.
> You mention that you do not understand overloading, well in essence
> creating an overload means that you are adding an additional function
> call to a class which has the same name that is distinguished by it's
> type signature.
> For instance
>
> public void SayHello()
> {SayHello();} //just calling overload method to save code in
> class
>
> public void SayHello(string name)
> { string display = "Hello";
> if name.Length > 0
> display += name;
> Console.WriteLi ne(display);
> }
>
> Which will mean that the Class would provide two method calls..
> 1 that allows you to SayHello without any arguments and the other to
> allow you to SayHello with a string argument.
>
> ***I think you are also getting a little bit confused with overloading
> and overriding - they are two DIFFERENT concepts. You should ideally
> read up on both since they are crucial to good OOP***
>
>
>
> "Thomas P. Skinner [MVP]" <to*@bu.edu> wrote in message
> news:uK******** ******@TK2MSFTN GP15.phx.gbl...
>> An overloaded method is a method that differs from all methods of the
>> same name in so far as it has a different number or types of its
>> arguments. A different return type does not constitute an overload.
>> If you get an error stating that no overload has 0 arguments then you
>> are calling a method with no arguments and you have no overloaded
>> method that takes zero arguments. Either instantiate the class with a
>> constructor call with arguments or provide an explicit constructor
>> with zero arguments. In C# if you provide an overloaded constructor
>> you no longer get a default constructor (zero arguments) and need to
>> provide one. I think this is your problem.
>>
>> Thomas P. Skinner [MVP]
>>
>> "Benny Raymond" <be***@pocketro cks.com> wrote in message
>> news:%2******** ********@tk2msf tngp13.phx.gbl. ..
>>> I'm trying to change the way a treeview works just a bit, i'm pretty
>>> new to C# and now i'm running into overloading. I tried the
>>> following code and it's yelling at me saying that no overload method
>>> takes 0 arguments.
>>>
>>> #region tViewNodeCollec tion
>>> public class tViewNodeCollec tion : TreeNodeCollect ion
>>> {
>>> private tView _owner;
>>> private tViewNode _parent;
>>> /// <summary>
>>> /// Create a collection within a tViewItem
>>> /// </summary>
>>> /// <param name="parent"></param>
>>> public tViewNodeCollec tion(tViewNode parent)
>>> {
>>> _parent = parent;
>>> }
>>> /// <summary>
>>> /// Create a new instance of tViewNodeCollec tion
>>> /// </summary>
>>> /// <param name="owner"></param>
>>> public tViewNodeCollec tion(tView owner)
>>> {
>>> _owner = owner;
>>> }
>>> /// <summary>
>>> /// Create a new instance of tViewNodeCollec tion
>>> /// </summary>
>>> /// <param name="owner"></param>
>>> public tViewNodeCollec tion(tView owner, tViewNode parent)
>>> {
>>> _owner = owner;
>>> _parent = parent;
>>> }
>>> }
>>> #endregion
>>>
>>>
>>> so then I tried a series of different :this(something ) but that
>>> started scaring me since I really don't understand overloading -
>>> Could someone shed some light on this for me?
>>
>>
>
>
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