VB and implicit conversions

[Chad Z. Hower aka Kudzu]

I have an implicit conversion set up in an assembly from a Stream to
something else. In C#, it works. In VB it does not.

Does VB support implicit conversions? And if so any idea why it would work in
a C# program but not VB?
--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programmin g is an art form that fights back"
ELKNews - Get your free copy at http://www.atozedsoftware.com

[Klaus Löffelmann]

Chad,

no, VB doesn't support implicit castings in the current version. That is, it
doesn't support implicit castings from non-primitive types. Only Whidbey
will support that (and hopefully it will be produce code that is compatible
with the code generated by C# when using the implicit operator); in the
meanwhile, you have to use the DirectCast keyword to unbox an object.

Klaus

"Chad Z. Hower aka Kudzu" <cp**@hower.org > schrieb im Newsbeitrag
news:Xn******** **********@127. 0.0.1...

I have an implicit conversion set up in an assembly from a Stream to
something else. In C#, it works. In VB it does not.

Does VB support implicit conversions? And if so any idea why it would work in a C# program but not VB?
--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programmin g is an art form that fights back"
ELKNews - Get your free copy at http://www.atozedsoftware.com

[Chad Z. Hower aka Kudzu]

"Klaus Löffelmann" <fo***********@ loeffelmann.de> wrote in
news:40******** **************@ news.freenet.de :

Whidbey will support that (and hopefully it will be produce code that is
compatible with the code generated by C# when using the implicit
operator); in the meanwhile, you have to use the DirectCast keyword to
unbox an object.

Ack. :(

I understand that there are differences between VB and C#. But how can MS
leave someting like this out? Esp from VB, the king language of anti type
safety. Where you could string = integer. :(

Can you give me an example of DirectCast?

--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programmin g is an art form that fights back"
ELKNews - Get your free copy at http://www.atozedsoftware.com

[Armin Zingler]

"Chad Z. Hower aka Kudzu" <cp**@hower.org > schrieb

I have an implicit conversion set up in an assembly from a Stream to
something else. In C#, it works. In VB it does not.

Does VB support implicit conversions? And if so any idea why it would
work in a C# program but not VB?

Code?
--
Armin

How to quote and why:
http://www.plig.net/nnq/nquote.html
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[Cor]

Hi Kudzu,

Inclusive the integer to string, although it is originaly Armin territory
because of that sample.
:-))

Dim a As Object
a = 1
Dim b As Integer
b = DirectCast(a, Integer)
MessageBox.Show (b.ToString)

Cor

[Klaus Löffelmann]

Chad,

I wouldn't call VB the king language of anti type safety. At least, not
anymore. And, of course, only if you set

Option Strict True

at the beginning of each source file or in the project settings.With this
setting, you can only cast those types implicitly, which are implicitly
castable in C#, too.

To provide more background: VB internally uses a special flag to recognize a
type for casting implicitly. When you write a static operator implicit
function with C#, C# generates a procedure called op_implicit, if I remember
correctly. You can use this function from VB, too, but only by this name (so
it's not implicitly usable, obviously...)

However, you can't set the flag from C# (and, unfortunately, neither from
VB), so a type conversion could be done implicitly from VB.

But DirectCast works fine in VB:

Dim var as mySpecialObject =DirectCast(spe cialObjectBoxed InWhatEverType,
mySpecialObject )

Keep in mind, that DirectCast only does the same as the cast operator does
in C#: (In this example specialObjectBo xedInWhatEverTy pe boxed an object of
type mySpecialObject ). It just unboxes a type. If you really want to do a
type conversion from one type to another, you should provide a constructor
with a parameter for your class, you could use like this:

Dim var as new mySpecialObject (OtherSpecialOb jectToCastFrom) .

In the constructor for mySpecialObject provide the code for the actual
conversion.

Klaus.


"Chad Z. Hower aka Kudzu" <cp**@hower.org > schrieb im Newsbeitrag
news:Xn******** **********@127. 0.0.1...

"Klaus Löffelmann" <fo***********@ loeffelmann.de> wrote in
news:40******** **************@ news.freenet.de :

Whidbey will support that (and hopefully it will be produce code that is
compatible with the code generated by C# when using the implicit
operator); in the meanwhile, you have to use the DirectCast keyword to
unbox an object.

Ack. :(

I understand that there are differences between VB and C#. But how can MS
leave someting like this out? Esp from VB, the king language of anti type
safety. Where you could string = integer. :(

Can you give me an example of DirectCast?

--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programmin g is an art form that fights back"
ELKNews - Get your free copy at http://www.atozedsoftware.com

[Chad Z. Hower aka Kudzu]

"Cor" <no*@non.com> wrote in news:uS******** ******@TK2MSFTN GP12.phx.gbl:

Dim a As Object
a = 1
Dim b As Integer
b = DirectCast(a, Integer)
MessageBox.Show (b.ToString)

Thanks. A direct conversion will be much easier than that. :(

But thanks for the answer.
--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programmin g is an art form that fights back"
ELKNews - Get your free copy at http://www.atozedsoftware.com

[Chad Z. Hower aka Kudzu]

"Armin Zingler" <az*******@free net.de> wrote in news:uiS5Hoy5DH A.2392
@TK2MSFTNGP11.p hx.gbl:

Does VB support implicit conversions? And if so any idea why it would
work in a C# program but not VB?

Code?

Its the very last VB example here:
http://www.atozed.com/indy/Texts/VSIntro.iwp

You can see the C# version directly above it. The parameter type to the Get
method is Borland.VCL.Cla sses.TStrings, which has an implict operator added
to it that allows conversion to it from System.IO.Strea m.

It looks like VB users might have to do direct conversions, which at least is
easyer than the DirectBox exmaple posted here.

That is something like:

new TCLRStream(MySt ream)

instead of just:

MyStream

whenever TStrings is needed.
--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programmin g is an art form that fights back"
ELKNews - Get your free copy at http://www.atozedsoftware.com

[Chad Z. Hower aka Kudzu]

"Klaus Löffelmann" <fo***********@ loeffelmann.de> wrote in
news:40******** **************@ news.freenet.de :

I wouldn't call VB the king language of anti type safety. At least, not
anymore. And, of course, only if you set
Yes, its been cleaned up in .net. I just find it ironic that traditionaly
VB has been anything but typesafe, in fact explicitly breaking it. And now
that they've cleaned it up, they gave C# implicit covnersion, but not VB.
Option Strict True
Yes I have this. But its my understanding that this applies to being able
to put integers into short ints, and the type off poor variations that VB
used to be rampant with.
at the beginning of each source file or in the project settings.With
this setting, you can only cast those types implicitly, which are
implicitly castable in C#, too.
But it applies only to ordinals, etc AFAIK.
To provide more background: VB internally uses a special flag to
recognize a type for casting implicitly. When you write a static
operator implicit function with C#, C# generates a procedure called
op_implicit, if I remember correctly. You can use this function from VB,
too, but only by this name (so it's not implicitly usable, obviously...)
Yes, exactly. :)
However, you can't set the flag from C# (and, unfortunately, neither
from VB), so a type conversion could be done implicitly from VB.
Exactly the problem it seems. :(
But DirectCast works fine in VB:

Dim var as mySpecialObject =DirectCast(spe cialObjectBoxed InWhatEverType,
mySpecialObject )
specialObjectBo xedInWhatEverTy pe would be in my case System.IO.Strea m
(Source) or Borland.VCL.Cla sses.TStrings (Destination)?
Keep in mind, that DirectCast only does the same as the cast operator
does in C#: (In this example specialObjectBo xedInWhatEverTy pe boxed an
object of type mySpecialObject ). It just unboxes a type. If you really
Is this the destination type or the source tyep though?
want to do a type conversion from one type to another, you should
provide a constructor with a parameter for your class, you could use
like this:

Already have that, and thats what the implicit operator does. However the
point is that this conversion is used often to pass in an argument, and the
idea was to free the user from needing to know there was even a difference.

--
Chad Z. Hower (a.k.a. Kudzu) - http://www.hower.org/Kudzu/
"Programmin g is an art form that fights back"
ELKNews - Get your free copy at http://www.atozedsoftware.com

[Armin Zingler]

"Chad Z. Hower aka Kudzu" <cp**@hower.org > schrieb

"Armin Zingler" <az*******@free net.de> wrote in
news:uiS5Hoy5DH A.2392 @TK2MSFTNGP11.p hx.gbl:

Does VB support implicit conversions? And if so any idea why it
would work in a C# program but not VB?

Code?

Its the very last VB example here:
http://www.atozed.com/indy/Texts/VSIntro.iwp

You can see the C# version directly above it. The parameter type to
the Get method is Borland.VCL.Cla sses.TStrings, which has an implict
operator added to it that allows conversion to it from
System.IO.Strea m.

It looks like VB users might have to do direct conversions, which at
least is easyer than the DirectBox exmaple posted here.

That is something like:

new TCLRStream(MySt ream)

instead of just:

MyStream

whenever TStrings is needed.

What is an "implicit operator"? Currently I don't understand the problem.
I'm happy now that I have to cast explicitly, otherwise casting errors might
occur at runtime because I don't get a error message at compile time.
--
Armin

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