Lets consider a class called Currency. This class must be the responsible for
taking care of all calculations over currency exchanges, in such a way that I
pass values in Euros and it returns the converted value in Dollar for
example...
Well, I might do this in 2 ways, as below:
1) I create a method like this:
double ConvertValue (double OriginalValue) {
// here I compute the value
return ComputedValue;
}
2) I create the method like this:
bool ConvertValue (double OriginalValue) {
// here I load private attribute ConvertedValue
ConvertedValue = ComputedValue
return OK;
}
In the first case I returned value in the method itself, in second case I
loaded the value in a private attribute. In second case the client method
would have to execute ConvertValue and then ask for property value. In first
case, the returned value would come in the method return itself....
What is the best approach? Are there special situations in which we should
use one or another??
Aug 12 '06
17  1530 
Well Cor,
Thank you for the information on currency class/methods, I will take a look
at it...
But the example I put there was only to expose my concern on how I should
proceed when using properties (more elegant) vs returning values directly in
method return.
AFAIK, one big difference is that properties enable us to
use n times the value in its instance, without having to call the method
again (something like keeping its state).
Besides, properties might be welcome when we return more than
1 value in the same method. In this case, instead of using ref values, we
might load n properties and then retrieve them right afterwards...
Some fellows in this post have helped me posting that this True/False return
is not good, it should be replaced by exception control. That gives me even
less argument to choose the property way in cases I return just 1 value...
However I cant figure out those strict situations where I should choose one
or another...
"Cor Ligthert [MVP]" wrote:
Bruce,
I definitly would not make a class name Currency, the currencymanager it is
an important class that already exist to get the current rows in the
system.data namespace. I have seen that this currencymanager gives often
misunderstandin gs, but I would not make that more worse.
http://msdn.microsoft.com/library/de...classtopic.asp
Therefore I would name it at least LocalizedCurren cy or something.
Than it is of couse easy to return in that class the needed localized value
based on the localized settings of the computer.
The currencysymbol and other things are already in this and related member.
http://msdn2.microsoft.com/en-us/lib...ncysymbol.aspx
I hope this helps,
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:E0******** *************** ***********@mic rosoft.com...
Lets consider a class called Currency. This class must be the responsible
for
taking care of all calculations over currency exchanges, in such a way
that I
pass values in Euros and it returns the converted value in Dollar for
example...
Well, I might do this in 2 ways, as below:
1) I create a method like this:
double ConvertValue (double OriginalValue) {
// here I compute the value
return ComputedValue;
}
2) I create the method like this:
bool ConvertValue (double OriginalValue) {
// here I load private attribute ConvertedValue
ConvertedValue = ComputedValue
return OK;
}
In the first case I returned value in the method itself, in second case I
loaded the value in a private attribute. In second case the client method
would have to execute ConvertValue and then ask for property value. In
first
case, the returned value would come in the method return itself....
What is the best approach? Are there special situations in which we should
use one or another??
Bruce One <ra**@virtualso ftware.com.brwr ote:
But the example I put there was only to expose my concern on how I should
proceed when using properties (more elegant) vs returning values directly in
method return.
You should use properties when they are:
1) Logically attributes of the class, i.e. similar to fields
2) Cheap to calculate and return
3) If reading doesn't modify the observable state of the class
4) If writeable, then writing and subsequently reading gives the same
value (i.e. { a.Prop = 42; Debug.Assert(a. Prop == 42); }), unless
writing the property throws an exception because of a problem with the
value.
5) No arguments are required to calculate the return value
When using properties that take arguments (i.e. 'public int this[int
index] { get; set; }'), you should restrict them to things like lists
and dictionaries, things that are usually collections and indexed by key
or index.
-- Barry
-- http://barrkel.blogspot.com/
Kelly,
Could your explain better points 3 and 4?
"Barry Kelly" wrote:
Bruce One <ra**@virtualso ftware.com.brwr ote:
But the example I put there was only to expose my concern on how I should
proceed when using properties (more elegant) vs returning values directly in
method return.
You should use properties when they are:
1) Logically attributes of the class, i.e. similar to fields
2) Cheap to calculate and return
3) If reading doesn't modify the observable state of the class
4) If writeable, then writing and subsequently reading gives the same
value (i.e. { a.Prop = 42; Debug.Assert(a. Prop == 42); }), unless
writing the property throws an exception because of a problem with the
value.
5) No arguments are required to calculate the return value
When using properties that take arguments (i.e. 'public int this[int
index] { get; set; }'), you should restrict them to things like lists
and dictionaries, things that are usually collections and indexed by key
or index.
-- Barry
--
http://barrkel.blogspot.com/
Bruce,
I would forever choose for a property if possible (in connection to my
previous reply) all was it alone that those are bindable, showable in a
property grid and serializable. Beside that do *I* find the text showed in
intellisence mostly standard better to understand from those.
When you want a direct answer, I never would take your method 2. It is only
confusing especially if the method is longer.
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:82******** *************** ***********@mic rosoft.com...
Well Cor,
Thank you for the information on currency class/methods, I will take a
look
at it...
But the example I put there was only to expose my concern on how I should
proceed when using properties (more elegant) vs returning values directly
in
method return.
AFAIK, one big difference is that properties enable us to
use n times the value in its instance, without having to call the method
again (something like keeping its state).
Besides, properties might be welcome when we return more than
1 value in the same method. In this case, instead of using ref values, we
might load n properties and then retrieve them right afterwards...
Some fellows in this post have helped me posting that this True/False
return
is not good, it should be replaced by exception control. That gives me
even
less argument to choose the property way in cases I return just 1 value...
However I cant figure out those strict situations where I should choose
one
or another...
"Cor Ligthert [MVP]" wrote:
>Bruce,
I definitly would not make a class name Currency, the currencymanager it
is
an important class that already exist to get the current rows in the
system.data namespace. I have seen that this currencymanager gives often
misunderstandi ngs, but I would not make that more worse.
http://msdn.microsoft.com/library/de...classtopic.asp
Therefore I would name it at least LocalizedCurren cy or something.
Than it is of couse easy to return in that class the needed localized
value
based on the localized settings of the computer.
The currencysymbol and other things are already in this and related
member.
http://msdn2.microsoft.com/en-us/lib...ncysymbol.aspx
I hope this helps,
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:E0******* *************** ************@mi crosoft.com...
Lets consider a class called Currency. This class must be the
responsible
for
taking care of all calculations over currency exchanges, in such a way
that I
pass values in Euros and it returns the converted value in Dollar for
example...
Well, I might do this in 2 ways, as below:
1) I create a method like this:
double ConvertValue (double OriginalValue) {
// here I compute the value
return ComputedValue;
}
2) I create the method like this:
bool ConvertValue (double OriginalValue) {
// here I load private attribute ConvertedValue
ConvertedValue = ComputedValue
return OK;
}
In the first case I returned value in the method itself, in second case
I
loaded the value in a private attribute. In second case the client
method
would have to execute ConvertValue and then ask for property value. In
first
case, the returned value would come in the method return itself....
What is the best approach? Are there special situations in which we
should
use one or another??
Cor,
So if you dont like executing a void method and then calling for the
property return, what would the best approach?
My great fear about using properties, instead of returning in method return
itself is that client code is unaware of what properties exaclty he should
reference to get the values he wants...
"Cor Ligthert [MVP]" wrote:
Bruce,
I would forever choose for a property if possible (in connection to my
previous reply) all was it alone that those are bindable, showable in a
property grid and serializable. Beside that do *I* find the text showed in
intellisence mostly standard better to understand from those.
When you want a direct answer, I never would take your method 2. It is only
confusing especially if the method is longer.
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:82******** *************** ***********@mic rosoft.com...
Well Cor,
Thank you for the information on currency class/methods, I will take a
look
at it...
But the example I put there was only to expose my concern on how I should
proceed when using properties (more elegant) vs returning values directly
in
method return.
AFAIK, one big difference is that properties enable us to
use n times the value in its instance, without having to call the method
again (something like keeping its state).
Besides, properties might be welcome when we return more than
1 value in the same method. In this case, instead of using ref values, we
might load n properties and then retrieve them right afterwards...
Some fellows in this post have helped me posting that this True/False
return
is not good, it should be replaced by exception control. That gives me
even
less argument to choose the property way in cases I return just 1 value...
However I cant figure out those strict situations where I should choose
one
or another...
"Cor Ligthert [MVP]" wrote:
Bruce,
I definitly would not make a class name Currency, the currencymanager it
is
an important class that already exist to get the current rows in the
system.data namespace. I have seen that this currencymanager gives often
misunderstandin gs, but I would not make that more worse.
http://msdn.microsoft.com/library/de...classtopic.asp
Therefore I would name it at least LocalizedCurren cy or something.
Than it is of couse easy to return in that class the needed localized
value
based on the localized settings of the computer.
The currencysymbol and other things are already in this and related
member.
http://msdn2.microsoft.com/en-us/lib...ncysymbol.aspx
I hope this helps,
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:E0******** *************** ***********@mic rosoft.com...
Lets consider a class called Currency. This class must be the
responsible
for
taking care of all calculations over currency exchanges, in such a way
that I
pass values in Euros and it returns the converted value in Dollar for
example...
Well, I might do this in 2 ways, as below:
1) I create a method like this:
double ConvertValue (double OriginalValue) {
// here I compute the value
return ComputedValue;
}
2) I create the method like this:
bool ConvertValue (double OriginalValue) {
// here I load private attribute ConvertedValue
ConvertedValue = ComputedValue
return OK;
}
In the first case I returned value in the method itself, in second case
I
loaded the value in a private attribute. In second case the client
method
would have to execute ConvertValue and then ask for property value. In
first
case, the returned value would come in the method return itself....
What is the best approach? Are there special situations in which we
should
use one or another??
Bruce,
Using intelisense is the simplest method to tell the client all he wants to
know, it can be showed in the propertygrid and while selecting it in
intelisence by the comments. http://msdn2.microsoft.com/en-us/library/z04awywx.aspx
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:A4******** *************** ***********@mic rosoft.com...
Cor,
So if you dont like executing a void method and then calling for the
property return, what would the best approach?
My great fear about using properties, instead of returning in method
return
itself is that client code is unaware of what properties exaclty he should
reference to get the values he wants...
"Cor Ligthert [MVP]" wrote:
>Bruce,
I would forever choose for a property if possible (in connection to my
previous reply) all was it alone that those are bindable, showable in a
property grid and serializable. Beside that do *I* find the text showed
in
intellisence mostly standard better to understand from those.
When you want a direct answer, I never would take your method 2. It is
only
confusing especially if the method is longer.
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:82******* *************** ************@mi crosoft.com...
Well Cor,
Thank you for the information on currency class/methods, I will take a
look
at it...
But the example I put there was only to expose my concern on how I
should
proceed when using properties (more elegant) vs returning values
directly
in
method return.
AFAIK, one big difference is that properties enable us to
use n times the value in its instance, without having to call the
method
again (something like keeping its state).
Besides, properties might be welcome when we return more than
1 value in the same method. In this case, instead of using ref values,
we
might load n properties and then retrieve them right afterwards...
Some fellows in this post have helped me posting that this True/False
return
is not good, it should be replaced by exception control. That gives me
even
less argument to choose the property way in cases I return just 1
value...
However I cant figure out those strict situations where I should choose
one
or another...
"Cor Ligthert [MVP]" wrote:
Bruce,
I definitly would not make a class name Currency, the currencymanager
it
is
an important class that already exist to get the current rows in the
system.data namespace. I have seen that this currencymanager gives
often
misunderstandi ngs, but I would not make that more worse.
http://msdn.microsoft.com/library/de...classtopic.asp
Therefore I would name it at least LocalizedCurren cy or something.
Than it is of couse easy to return in that class the needed localized
value
based on the localized settings of the computer.
The currencysymbol and other things are already in this and related
member.
http://msdn2.microsoft.com/en-us/lib...ncysymbol.aspx
I hope this helps,
Cor
"Bruce One" <ra**@virtualso ftware.com.brsc hreef in bericht
news:E0******* *************** ************@mi crosoft.com...
Lets consider a class called Currency. This class must be the
responsible
for
taking care of all calculations over currency exchanges, in such a
way
that I
pass values in Euros and it returns the converted value in Dollar
for
example...
Well, I might do this in 2 ways, as below:
1) I create a method like this:
double ConvertValue (double OriginalValue) {
// here I compute the value
return ComputedValue;
}
2) I create the method like this:
bool ConvertValue (double OriginalValue) {
// here I load private attribute ConvertedValue
ConvertedValue = ComputedValue
return OK;
}
In the first case I returned value in the method itself, in second
case
I
loaded the value in a private attribute. In second case the client
method
would have to execute ConvertValue and then ask for property value.
In
first
case, the returned value would come in the method return itself....
What is the best approach? Are there special situations in which we
should
use one or another??
Bruce One <ra**@virtualso ftware.com.brwr ote:
Kelly,
My name is Barry!
Could your explain better points 3 and 4?
3) If reading doesn't modify the observable state of the class
Just reading a property shouldn't change the property. For example:
Button b = new Button();
// ...
string text = b.Text;
This action (reading b.Text, which is a property) shouldn't change the
property. Another example:
IEnumerator x = new List().GetEnume rator();
bool b = x.MoveNext();
This action, MoveNext(), changes the enumerator - it moves it forward
one. Therefore it shouldn't be a property, it should be a method (which
it is).
4) If writeable, then writing and subsequently reading gives the same
value (i.e. { a.Prop = 42; Debug.Assert(a. Prop == 42); }), unless
writing the property throws an exception because of a problem with the
value.
When there is a property, people expect this:
b.Name = "foo";
if (b.Name != "foo")
throw new Exception("Some thing went wrong!");
If this code would throw an exception for your property, then it
shouldn't be a property - it should be a method.
This only matters if the property is writeable - that is, it has a 'set'
method.
-- Barry
-- http://barrkel.blogspot.com/
Barry, sorry for misusing your name.
I think I quite understood your points, I will try to fit our cases in one
of these situations.
Thanks!
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