Bug in DirectCast() ?

[Guido Kraus]

I tried this VB.NET 2003 (.Net runtime 1.1):

Dim o As Object = DirectCast(Nothing, HashTable)
If IsNothing(o) Then
Debug.WriteLine("Nothing")
Else
Debug.WriteLine("Something")
End If

Guess what: o is not Nothing!
Is this a bug or a feature? By the way: CType(Nothing, HashTable) returns
Nothing as I would expect.

Guido

 

[Bill McCarthy]

hi Guido,

recheck your code. I tested it and cannot reproduce. I get o is Nothing.


Bill.

 

[Herfried K. Wagner [MVP]]

I tried this VB.NET 2003 (.Net runtime 1.1):

Dim o As Object = DirectCast(Nothing, HashTable)
If IsNothing(o) Then
Debug.WriteLine("Nothing")
Else
Debug.WriteLine("Something")
End If

Guess what: o is not Nothing!
Is this a bug or a feature? By the way: CType(Nothing, HashTable) returns
Nothing as I would expect.

I am not able to repro that in .NET 1.1, VB.NET 2003.

 

[Bill McCarthy]

Hi Guido,

Yeh, I get the same in the watch window, but I still get the result to be
Nothing when actually run:
e.g:

Console.Writeline( DirectCast(Nothing, Hashtable) Is Nothing)

returns True.

What does your watch window say for :
DirectCast(Nothing, Hashtable) Is Nothing

 

[Cor]

Hi Guido,
Dim o As Object = DirectCast(Nothing, Hashtable)
Dim m As Object = CType(Nothing, Hashtable)
If m Is o Then
MessageBox.Show("both the same")
End If

both the same is showed (and they are nothing)

Cor

 

[Guido Kraus]

Hi Bill,

you are right.
DirectCast(Nothing, Hashtable) Is Nothing correctly returns Nothing and the
example I gave also works correctly. However, the watch window and the
variable tooltips obviously have a problem because they display {Length = 0}
instead of Nothing.

Guido

 

[Cor]

Guido,

I remember me that shortly ago Jay B. Harlow has told something about this
windows

I found the article here

http://tinyurl.com/2lrb4

Cor

 

[Herfried K. Wagner [MVP]]

you are right.
DirectCast(Nothing, Hashtable) Is Nothing correctly returns Nothing and the
example I gave also works correctly. However, the watch window and the
variable tooltips obviously have a problem because they display {Length = 0}
instead of Nothing.

Yep. The watch window and the tooltips don't always show the right
data.