Q re: Type casting

[Simon Woods]

Another quick q - sorry to trouble, again ...

If I have a class as follows:

Public Class MyClass(Of T)

Private _myValue as T
Public Property MyValue() as T
Get
Return _myValue
End Get
Set (value as T)
_myValue = value
End Set
End Property

Public Readonly Property MyValue1() as Object
Get
Return _myValue
End Get
End Property

End Class

Dim _myClass as New MyClass(Of String)

What is happening, in terms of typecasting/performance (or perhaps
wrapping), when I retrieve the _myValue out of the MyValue1 Getter.

Thx

Simon

[Herfried K. Wagner [MVP]]

Re: Type casting

"Simon Woods" <simonjwoods@ho tmail.comschrie b:

Public Class MyClass(Of T)
>
Private _myValue as T
Public Property MyValue() as T
Get
Return _myValue
End Get
Set (value as T)
_myValue = value
End Set
End Property
>
Public Readonly Property MyValue1() as Object
Get
Return _myValue
End Get
End Property
>
End Class
>
Dim _myClass as New MyClass(Of String)
>
What is happening, in terms of typecasting/performance (or perhaps
wrapping), when I retrieve the _myValue out of the MyValue1 Getter.

You can examine the IL generated by the compiler using ILDASM which comes
with the .NET Framework SDK or Lutz Roeder's Reflector for .NET. In the
scenario you describe a simple (implicit) upcast to 'Object' is performed,
which is not costly at all if the type is a reference type, which is the
case for 'String'.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>

[Simon Woods]

Re: Type casting

Herfried K. Wagner [MVP] wrote:

"Simon Woods" <simonjwoods@ho tmail.comschrie b:

>Public Class MyClass(Of T)
>>
> Private _myValue as T
> Public Property MyValue() as T
>Get
> Return _myValue
> End Get
>Set (value as T)
> _myValue = value
>End Set
> End Property
>>
> Public Readonly Property MyValue1() as Object
>Get
> Return _myValue
> End Get
> End Property
>>
>End Class
>>
>Dim _myClass as New MyClass(Of String)
>>
>What is happening, in terms of typecasting/performance (or perhaps
>wrapping), when I retrieve the _myValue out of the MyValue1 Getter.

>
You can examine the IL generated by the compiler using ILDASM which
comes with the .NET Framework SDK or Lutz Roeder's Reflector for .NET.
In the scenario you describe a simple (implicit) upcast to 'Object' is
performed, which is not costly at all if the type is a reference type,
which is the case for 'String'.
>

Excellent ... thanks for the tip