Hi guys,
I work mostly with vb.net and today only started doping some C#. Can
some translate the following vb code in C#
'--Here conn is connection object
If Not (conn Is Nothing) Then
'-----
End If

if (conn != null)
{
...do something
}

null is the c# equivalent of VB Nothing
! is c# equivalent of VB Not

Hope that helps
Mark R Dawson
http://www.markdawson.org



"dot Net Pa Ji" wrote:

> Hi guys,
> I work mostly with vb.net and today only started doping some C#. Can
> some translate the following vb code in C#
> '--Here conn is connection object
> If Not (conn Is Nothing) Then
> '-----
> End If
>
>
>

> If Not (conn Is Nothing) Then
> '-----
> End If
>
if (!(conn == null)){//so something
}

I would do it in VBNet as well as this bellow

If Not conn Is Nothing then
'do something
End if

Than it becomes more as Mark showed you.

I hope this helps,

Cor

> null is the c# equivalent of VB Nothing

While that is true for reference types, Nothing is valid for value
types as well in VB. I *believe* that the default value for a member
variable of any particular type is the value of VB.NET's Nothing for
that same type - so for boolean it's false, for int it's 0 etc.

Not relevant in this particular example, but worth noting.

Jon

Hi Robinhood.

For your information in VB.Net is a difference between = Nothing and Is
Nothing.

= Nothing means for a value type empty or default
Is Nothing means for a reference type no reference.

By instance a string can have both

Setting to nothing is for both =

(Robin Hood because he came from Nothingham)

:-)

Cor

"Jon Skeet [C# MVP]" <(E-Mail Removed)> schreef in bericht
news:(E-Mail Removed)...
>> null is the c# equivalent of VB Nothing
>
> While that is true for reference types, Nothing is valid for value
> types as well in VB. I *believe* that the default value for a member
> variable of any particular type is the value of VB.NET's Nothing for
> that same type - so for boolean it's false, for int it's 0 etc.
>
> Not relevant in this particular example, but worth noting.
>
> Jon
>

Thanks for the information.
---DNPJ
"Cor Ligthert [MVP]" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hi Robinhood.
>
> For your information in VB.Net is a difference between = Nothing and Is
> Nothing.
>
> = Nothing means for a value type empty or default
> Is Nothing means for a reference type no reference.
>
> By instance a string can have both
>
> Setting to nothing is for both =
>
> (Robin Hood because he came from Nothingham)
>
> :-)
>
> Cor
>
> "Jon Skeet [C# MVP]" <(E-Mail Removed)> schreef in bericht
> news:(E-Mail Removed)...
>>> null is the c# equivalent of VB Nothing
>>
>> While that is true for reference types, Nothing is valid for value
>> types as well in VB. I *believe* that the default value for a member
>> variable of any particular type is the value of VB.NET's Nothing for
>> that same type - so for boolean it's false, for int it's 0 etc.
>>
>> Not relevant in this particular example, but worth noting.
>>
>> Jon
>>
>
>

Cor Ligthert [MVP] <(E-Mail Removed)> wrote:
> For your information in VB.Net is a difference between = Nothing and Is
> Nothing.
>
> = Nothing means for a value type empty or default
> Is Nothing means for a reference type no reference.
>
> By instance a string can have both

What makes a string different from other reference types though? That
doesn't make sense to me. Is it just to make it more like VB6?

--
Jon Skeet - <(E-Mail Removed)>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

On 2005-09-21, Jon Skeet C# MVP <(E-Mail Removed)> wrote:
> Cor Ligthert [MVP] <(E-Mail Removed)> wrote:
>> For your information in VB.Net is a difference between = Nothing and Is
>> Nothing.
>>
>> = Nothing means for a value type empty or default
>> Is Nothing means for a reference type no reference.
>>
>> By instance a string can have both
>
> What makes a string different from other reference types though? That
> doesn't make sense to me. Is it just to make it more like VB6?

Pretty much. It's to make string compares work in a way similar to the
way they did in VB6. String comparisons are special-cased in VB.Net not
just for the reference/value type/empty means nothing/ issue, but
because VB also needs to support things like the Option Compare
statement, and there's some automatic culture stuff that's handled
during string compares (I doubt that one in a thousand VB developers
could tell you what String = String actually does in any detail.).

In VB.Net, for a string s

If s Is Nothing
works identically to if(s == null)

If s = Nothing

is equivalent to if(s == null || s == String.Empty)

Note this isn't polymorphic, you can't do

Dim s As Object = "Hello World"

If s = Nothing

That won't compile, because "= Nothing" is not valid for reference
types, except for Strings.