Casting?

[Shannon Richards]

Hello: I am confused about casting...

Option Strict = ON

Example1:
---------------
When I say something like this...

Dim lo_Foo = New Foo
Dim lo_Obj as Object = lo_Foo

Works Fine!
Example2:
---------------
When I say something like this...

Dim lo_Foo = New Foo

OutPutObj(lo_Fo o)

Public Sub OutPutObj(ao_Ob j as Object)
...
End Sub

Compile Error: "Option Strict ON disallows implicit conversion from
System.Object to type Foo"

Isn't there an implicit conversion in the first example when the variable of
type object is set to the instance of Foo???

Thank you,
Shannon Richards
BBA, AIT, MCP

[Herfried K. Wagner [MVP]]

"Shannon Richards" <sr**********@h otmail.com> schrieb:

Hello: I am confused about casting...

Option Strict = ON

Example1:
---------------
When I say something like this...

Dim lo_Foo = New Foo
Dim lo_Obj as Object = lo_Foo

Works Fine!
Example2:
---------------
When I say something like this...

Dim lo_Foo = New Foo

OutPutObj(lo_Fo o)

Public Sub OutPutObj(ao_Ob j as Object)
...
End Sub

Compile Error: "Option Strict ON disallows implicit conversion from
System.Object to type Foo"

Where does it say that? It doesn't say that for the code you posted.

The message will be shown when casting from a base type to one of its
derived type, but not when "casting" from the derived type to the base type.
That's why the cast to 'Object' will always work.

--
Herfried K. Wagner [MVP]
<URL:http://dotnet.mvps.org/>

[Scott M.]

All types of sedan automobiles are cars, but not all cars are sedan
automobiles.

You can cast a sedan as a car, but you can't cast a car as a sedan.

Get it?

"Shannon Richards" <sr**********@h otmail.com> wrote in message
news:uU******** *****@TK2MSFTNG P10.phx.gbl...

Hello: I am confused about casting...

Option Strict = ON

Example1:
---------------
When I say something like this...

Dim lo_Foo = New Foo
Dim lo_Obj as Object = lo_Foo

Works Fine!
Example2:
---------------
When I say something like this...

Dim lo_Foo = New Foo

OutPutObj(lo_Fo o)

Public Sub OutPutObj(ao_Ob j as Object)
...
End Sub

Compile Error: "Option Strict ON disallows implicit conversion from
System.Object to type Foo"

Isn't there an implicit conversion in the first example when the variable
of type object is set to the instance of Foo???

Thank you,
Shannon Richards
BBA, AIT, MCP

[Ken Dopierala Jr.]

Hi Shannon,

Option Strict On doesn't allow late-binding. For some reason I believe the
compiler considers your first example either early-binding or allowed
late-binding and your second example illegal late-binding with Option Strict
On. I think that is what is going on but I'm not totally positive. My
point is that maybe this isn't a casting problem but a binding problem.
Some research on binding could give you a definitive answer. Good luck!
Ken.

--
Ken Dopierala Jr.
For great ASP.Net web hosting try:
http://www.webhost4life.com/default.asp?refid=Spinlight
If you sign up under me and need help, email me.

"Shannon Richards" <sr**********@h otmail.com> wrote in message
news:uU******** *****@TK2MSFTNG P10.phx.gbl...

Hello: I am confused about casting...

Option Strict = ON

Example1:
---------------
When I say something like this...

Dim lo_Foo = New Foo
Dim lo_Obj as Object = lo_Foo

Works Fine!
Example2:
---------------
When I say something like this...

Dim lo_Foo = New Foo

OutPutObj(lo_Fo o)

Public Sub OutPutObj(ao_Ob j as Object)
...
End Sub

Compile Error: "Option Strict ON disallows implicit conversion from
System.Object to type Foo"

Isn't there an implicit conversion in the first example when the variable of type object is set to the instance of Foo???

Thank you,
Shannon Richards
BBA, AIT, MCP

[Ken Dopierala Jr.]

Hi Shannon,

Option Strict On doesn't allow late-binding. For some reason I believe the
compiler considers your first example either early-binding or allowed
late-binding and your second example illegal late-binding with Option Strict
On. I think that is what is going on but I'm not totally positive. My
point is that maybe this isn't a casting problem but a binding problem.
Some research on binding could give you a definitive answer. Good luck!
Ken.

--
Ken Dopierala Jr.
For great ASP.Net web hosting try:
http://www.webhost4life.com/default.asp?refid=Spinlight
If you sign up under me and need help, email me.

"Shannon Richards" <sr**********@h otmail.com> wrote in message
news:uU******** *****@TK2MSFTNG P10.phx.gbl...

Hello: I am confused about casting...

Option Strict = ON

Example1:
---------------
When I say something like this...

Dim lo_Foo = New Foo
Dim lo_Obj as Object = lo_Foo

Works Fine!
Example2:
---------------
When I say something like this...

Dim lo_Foo = New Foo

OutPutObj(lo_Fo o)

Public Sub OutPutObj(ao_Ob j as Object)
...
End Sub

Compile Error: "Option Strict ON disallows implicit conversion from
System.Object to type Foo"

Isn't there an implicit conversion in the first example when the variable of type object is set to the instance of Foo???

Thank you,
Shannon Richards
BBA, AIT, MCP

[Mike McIntyre]

Shannon,

What is IncomeGateway? A Collection or ArrayList, or? Is it strongly type to only contain Income objects?

Same question for List?
--
Mike

Mike McIntyre
Visual Basic MVP
www.getdotnetcode.com
"Shannon Richards" <sr**********@h otmail.com> wrote in message news:OS******** ******@TK2MSFTN GP11.phx.gbl...
Here's what's really happening:

lo_Gateway.Inse rt(ByRef ao_Object As Object) - takes an argument of type object.

Since all reference types derive from object in .Net why is the compiler giving this error? Income is an Object...

[Mike McIntyre]

Shannon,

What is IncomeGateway? A Collection or ArrayList, or? Is it strongly type to only contain Income objects?

Same question for List?
--
Mike

Mike McIntyre
Visual Basic MVP
www.getdotnetcode.com
"Shannon Richards" <sr**********@h otmail.com> wrote in message news:OS******** ******@TK2MSFTN GP11.phx.gbl...
Here's what's really happening:

lo_Gateway.Inse rt(ByRef ao_Object As Object) - takes an argument of type object.

Since all reference types derive from object in .Net why is the compiler giving this error? Income is an Object...

[Jay B. Harlow [MVP - Outlook]]

Shannon,
In addition to the other comments (especially Nick's):

Insert is using ByRef, Do you really need ByRef here? Probably not.

ByVal & ByRef Parameters are independent of Reference & Value Types. All
parameters in VB.NET by default are passed ByVal, you should only pass a
parameter ByRef when you have to, which is when you need to modify the
callers variable.

A Reference Type is an object that exists on the heap. If I have a variable
that is a reference type and assign the variable to another variable. Both
variables will be pointing to the same object on the heap.

Dim x As Person
x = New Person()
Dim y As Person
y = x

Both x & y are the exact same Person object on the heap.

A Value Type does not live on the Heap. If I have a value type variable and
I assign it to another variable, a copy of the value is made.

Dim x As Integer
x = 100
Dim y As Integer
y = x

Although both x & y have the value 100, they are physically different values
as a copy was made.

Now when you pass a variable to a ByVal parameter a copy of the variable is
made. So for a Reference Type a copy of the reference is made, which means
there is still only one object on the heap & two references to that object.
For a Value Type a copy of the value is made.

When you pass a variable to a ByRef parameter a reference to that variable
is made. So for a Reference Type you have a reference to a reference to the
object, for a Value Type you have a reference to the value.

Remember ByVal & ByRef are how parameters are passed. Reference & Value
Types are how quantities are stored.

The following site also does a good job of explaining Reference & Value
types & ByRef & ByVal parameters.

http://www.yoda.arachsys.com/csharp/parameters.html
Hope this helps
Jay

"Shannon Richards" <sr**********@h otmail.com> wrote in message
news:OS******** ******@TK2MSFTN GP11.phx.gbl...
Here's what's really happening:

lo_Gateway.Inse rt(ByRef ao_Object As Object) - takes an argument of type
object.

Since all reference types derive from object in .Net why is the compiler
giving this error? Income is an Object...

[Jay B. Harlow [MVP - Outlook]]

Shannon,
In addition to the other comments (especially Nick's):

Insert is using ByRef, Do you really need ByRef here? Probably not.

ByVal & ByRef Parameters are independent of Reference & Value Types. All
parameters in VB.NET by default are passed ByVal, you should only pass a
parameter ByRef when you have to, which is when you need to modify the
callers variable.

A Reference Type is an object that exists on the heap. If I have a variable
that is a reference type and assign the variable to another variable. Both
variables will be pointing to the same object on the heap.

Dim x As Person
x = New Person()
Dim y As Person
y = x

Both x & y are the exact same Person object on the heap.

A Value Type does not live on the Heap. If I have a value type variable and
I assign it to another variable, a copy of the value is made.

Dim x As Integer
x = 100
Dim y As Integer
y = x

Although both x & y have the value 100, they are physically different values
as a copy was made.

Now when you pass a variable to a ByVal parameter a copy of the variable is
made. So for a Reference Type a copy of the reference is made, which means
there is still only one object on the heap & two references to that object.
For a Value Type a copy of the value is made.

When you pass a variable to a ByRef parameter a reference to that variable
is made. So for a Reference Type you have a reference to a reference to the
object, for a Value Type you have a reference to the value.

Remember ByVal & ByRef are how parameters are passed. Reference & Value
Types are how quantities are stored.

The following site also does a good job of explaining Reference & Value
types & ByRef & ByVal parameters.

http://www.yoda.arachsys.com/csharp/parameters.html
Hope this helps
Jay

"Shannon Richards" <sr**********@h otmail.com> wrote in message
news:OS******** ******@TK2MSFTN GP11.phx.gbl...
Here's what's really happening:

lo_Gateway.Inse rt(ByRef ao_Object As Object) - takes an argument of type
object.

Since all reference types derive from object in .Net why is the compiler
giving this error? Income is an Object...

[Shannon Richards]

Hello: Thank you all for your fantastic comments. I understand more about
the issue now.

One additional question...
When dealing with reference types as parameters. Is it more efficient to
code the parameter as ByRef since ByVal will end up creating another pointer
to the reference type being passed into the method?

Thank you,
Shannon
"Jay B. Harlow [MVP - Outlook]" <Ja************ @msn.com> wrote in message
news:eE******** ******@tk2msftn gp13.phx.gbl...

Shannon,
In addition to the other comments (especially Nick's):

Insert is using ByRef, Do you really need ByRef here? Probably not.

ByVal & ByRef Parameters are independent of Reference & Value Types. All
parameters in VB.NET by default are passed ByVal, you should only pass a
parameter ByRef when you have to, which is when you need to modify the
callers variable.

A Reference Type is an object that exists on the heap. If I have a
variable
that is a reference type and assign the variable to another variable. Both
variables will be pointing to the same object on the heap.

Dim x As Person
x = New Person()
Dim y As Person
y = x

Both x & y are the exact same Person object on the heap.

A Value Type does not live on the Heap. If I have a value type variable
and
I assign it to another variable, a copy of the value is made.

Dim x As Integer
x = 100
Dim y As Integer
y = x

Although both x & y have the value 100, they are physically different
values
as a copy was made.

Now when you pass a variable to a ByVal parameter a copy of the variable
is
made. So for a Reference Type a copy of the reference is made, which means
there is still only one object on the heap & two references to that
object.
For a Value Type a copy of the value is made.

When you pass a variable to a ByRef parameter a reference to that variable
is made. So for a Reference Type you have a reference to a reference to
the
object, for a Value Type you have a reference to the value.

Remember ByVal & ByRef are how parameters are passed. Reference & Value
Types are how quantities are stored.

The following site also does a good job of explaining Reference & Value
types & ByRef & ByVal parameters.

http://www.yoda.arachsys.com/csharp/parameters.html
Hope this helps
Jay

"Shannon Richards" <sr**********@h otmail.com> wrote in message
news:OS******** ******@TK2MSFTN GP11.phx.gbl...
Here's what's really happening:

lo_Gateway.Inse rt(ByRef ao_Object As Object) - takes an argument of type
object.

Since all reference types derive from object in .Net why is the compiler
giving this error? Income is an Object...