String.Format()

[Phill]

[How come you can do this]:

string.Format(" MyString {0}", var);

[But you can't do this]:

String str = "MyString {0}";
str.Format(var) ;

In otherwords why is Format a method of the string class but it can't
be used on an instance of the string class?

[Mattias Sjögren]

Re: String.Format()

[color=blue]
>In otherwords why is Format a method of the string class but it can't
>be used on an instance of the string class?[/color]

Because it's static.



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Lord2702]

Re: String.Format()

Try this:

Int32 Num = 99;
String str = "";

str = str.Format("Hel lo: {0}", Num);

str ===> "Hello: 99"

Eventhough a method is static you can access that method with its instance,
though, method is static an instance is NOT REQUIRED,

Good Luck !

"Phill" <wackyphill@yah oo.com> wrote in message
news:ac94631d.0 409181538.7b1e9 c37@posting.goo gle.com...[color=blue]
> [How come you can do this]:
>
> string.Format(" MyString {0}", var);
>
> [But you can't do this]:
>
> String str = "MyString {0}";
> str.Format(var) ;
>
> In otherwords why is Format a method of the string class but it can't
> be used on an instance of the string class?[/color]

[Nadav]

Re: String.Format()

I think the question is
WHY is Format static?

Why can't you do:

string fmt="<%d>";
string result=fmt.Form at(2); // => result="<2>";

Why do you have to write:

string result=string.F ormat(fmt,2);

Why is 'Replace()' (replace a substring with a string) a method of the
string instance,
but 'Format()' (replace format place holders with values) a static method?

Nadav

[Jon Skeet [C# MVP]]

Re: String.Format()

Lord2702 <Lord2702@MSN.c om> wrote:[color=blue]
> Int32 Num = 99;
> String str = "";
>
> str = str.Format("Hel lo: {0}", Num);
>
> str ===> "Hello: 99"[/color]

No, that doesn't compile.
[color=blue]
> Eventhough a method is static you can access that method with its instance,[/color]

No you can't.
[color=blue]
> though, method is static an instance is NOT REQUIRED,[/color]

It's not only not required, it's prohibited in C# (thank goodness -
this is one of the flaws in Java).

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too

[Phill]

Re: String.Format()

"Lord2702" <Lord2702@MSN.c om> wrote in message news:<#A06RignE HA.3628@TK2MSFT NGP09.phx.gbl>. ..[color=blue]
> Try this:
>
> Int32 Num = 99;
> String str = "";
>
> str = str.Format("Hel lo: {0}", Num);
>
> str ===> "Hello: 99"
>
> Eventhough a method is static you can access that method with its instance,
> though, method is static an instance is NOT REQUIRED,
>
> Good Luck ![/color]

You Example causes the following Error In VS 2002:

Static member 'string.Format( string, object)' cannot be accessed with
an instance reference; qualify it with a type name instead

[Lord2702]

Re: String.Format()

I am sorry ! I actually, test the example in Managed Visual C++ and send you
the C# code, just converting it. But today I check it is not even possible
to access the static method, as Intelliscence will not show the static
method with instatnce variable. This is agains the static rule, because in
Native C++, the rule is just like as I stated, i.e. Static method can be
access through instance variable, and with class name.

Sorry about that.

Good Luck !

"Phill" <wackyphill@yah oo.com> wrote in message
news:ac94631d.0 409190749.a0dd3 02@posting.goog le.com...[color=blue]
> "Lord2702" <Lord2702@MSN.c om> wrote in message[/color]
news:<#A06RignE HA.3628@TK2MSFT NGP09.phx.gbl>. ..[color=blue][color=green]
> > Try this:
> >
> > Int32 Num = 99;
> > String str = "";
> >
> > str = str.Format("Hel lo: {0}", Num);
> >
> > str ===> "Hello: 99"
> >
> > Eventhough a method is static you can access that method with its[/color][/color]
instance,[color=blue][color=green]
> > though, method is static an instance is NOT REQUIRED,
> >
> > Good Luck ![/color]
>
> You Example causes the following Error In VS 2002:
>
> Static member 'string.Format( string, object)' cannot be accessed with
> an instance reference; qualify it with a type name instead[/color]

[Phill]

Re: String.Format()

"Lord2702" <Lord2702@MSN.c om> wrote in message news:<e1F4kynnE HA.3876@TK2MSFT NGP15.phx.gbl>. ..[color=blue]
> I am sorry ! I actually, test the example in Managed Visual C++ and send you
> the C# code, just converting it. But today I check it is not even possible
> to access the static method, as Intelliscence will not show the static
> method with instatnce variable. This is agains the static rule, because in
> Native C++, the rule is just like as I stated, i.e. Static method can be
> access through instance variable, and with class name.
>[/color]

Right, comming from A C++ background I would like static methods to be
accesible to instances of the class. I'm not sure I agree w/ John that
that is a flaw in C++ or Java. It seems to be reasonable to me that
you should be able to do this. But I'd be interested in an explanation
of why you think its a bad idea John.

[Daniel O'Connell [C# MVP]]

Re: String.Format()


"Phill" <wackyphill@yah oo.com> wrote in message
news:ac94631d.0 409192001.5507e 6c9@posting.goo gle.com...[color=blue]
> "Lord2702" <Lord2702@MSN.c om> wrote in message
> news:<e1F4kynnE HA.3876@TK2MSFT NGP15.phx.gbl>. ..[color=green]
>> I am sorry ! I actually, test the example in Managed Visual C++ and send
>> you
>> the C# code, just converting it. But today I check it is not even
>> possible
>> to access the static method, as Intelliscence will not show the static
>> method with instatnce variable. This is agains the static rule, because
>> in
>> Native C++, the rule is just like as I stated, i.e. Static method can be
>> access through instance variable, and with class name.
>>[/color]
>
> Right, comming from A C++ background I would like static methods to be
> accesible to instances of the class. I'm not sure I agree w/ John that
> that is a flaw in C++ or Java. It seems to be reasonable to me that
> you should be able to do this. But I'd be interested in an explanation
> of why you think its a bad idea John.[/color]

A static method and an instance method are two very different things. Static
methods do not interact with instance data and are expected to have either
global effects or effects on parameters, while instance methods interact
with instance data and are expected have local effects. The argument against
allowing access to static methods via an instance variable is basically
that, by calling through an instance, a static method looks like an instance
method and therefore the caller does not expect his call to have global
consequences.

I consider calling a static method via an instance to be as bad as, say,
using an instance method to maintain a static list. It just isn't a good
idea.

[Jon Skeet [C# MVP]]

Re: String.Format()

Phill <wackyphill@yah oo.com> wrote:[color=blue]
> Right, comming from A C++ background I would like static methods to be
> accesible to instances of the class. I'm not sure I agree w/ John that
> that is a flaw in C++ or Java. It seems to be reasonable to me that
> you should be able to do this. But I'd be interested in an explanation
> of why you think its a bad idea John.[/color]

It hides the fact that the method is static. This means that someone
reading the code might:

a) Expect the method to be called with respect to the particular
instance
b) Expect a NullReferenceEx ception if the expression used evaluates to
null
c) Expect polymorphism


Here's a sample piece of Java:

Thread t = new Thread(someRunn able);
t.Start();
t.Sleep(1000);

What does the third line do? It actually makes the current thread
sleep. That's not what the code implies though.

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

If replying to the group, please do not mail me too