Unreachable expression code detected

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teddysnips@hotmail.com - 21 Jun 2007 17:01 GMT

I'm new to C# - recent background mainly ASP.NET with VB.NET.

Anyhoot, I needed to create a C# statement analogous to VB's IIf:

VB.NET

Dim e As Boolean

e = IIf((CInt(MyVariable) > 0), True, False)

C#

bool e = ((int)MyVariable > 0) ? true : false;

It compiles and runs fine under C#, but the "false" word has a wiggly
green line underneath and the legend in the Warnings tab of the Errors
pane:

"Unreachable expression code detected"

Don't understand - can anyone shed light?

Thanks

Edward

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Marc Gravell - 21 Jun 2007 17:04 GMT

First - you can just use:

bool e = ((int)MyVariable > 0);

Now; how is MyVariable defined? This should be fine - however, if
MyVariable is a "const", then the compiler will be evaluating this at
compile-time, so yes: the warning is correct.

Marc

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Peter Bradley - 21 Jun 2007 17:10 GMT

You don't say what type MyVariable is, but it looks as though it casts to an
int OK.

So (int)MyVarialbe > 0 is already a boolean expression. Therefore I think
you only need:

bool e = (int)MyVariable > 0;

Of course if MyVariable is something that always resolves to a value greater
than zero when cast to an integer, then it will always resolve to true.

HTH

Peter

> I'm new to C# - recent background mainly ASP.NET with VB.NET.
>
[quoted text clipped - 21 lines]
>
> Edward

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teddysnips@hotmail.com - 22 Jun 2007 08:39 GMT

> You don't say what type MyVariable is, but it looks as though it casts to an
> int OK.
[quoted text clipped - 3 lines]
>
> bool e = (int)MyVariable > 0;

Doh! That's much more elegant. Thanks.

Edward

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Peter Bradley - 22 Jun 2007 19:41 GMT

Ysgrifennodd teddysnips@hotmail.com:

>> You don't say what type MyVariable is, but it looks as though it casts to an
>> int OK.
[quoted text clipped - 7 lines]
>
> Edward

The pleasure's mine

Peter

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Alun Harford - 21 Jun 2007 19:06 GMT

> I'm new to C# - recent background mainly ASP.NET with VB.NET.
>
[quoted text clipped - 17 lines]
>
> Don't understand - can anyone shed light?

The compiler knows that ((int)MyVariable > 0) is always true.

Alun Harford

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teddysnips@hotmail.com - 22 Jun 2007 08:38 GMT

> teddysn...@hotmail.com wrote:
> > I'm new to C# - recent background mainly ASP.NET with VB.NET.
[quoted text clipped - 20 lines]
>
> The compiler knows that ((int)MyVariable > 0) is always true.

But it isn't! MyVariable can (and sometimes is) exactly 0.

Edward

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Jon Skeet [C# MVP] - 22 Jun 2007 08:54 GMT

On Jun 22, 8:38 am, teddysn...@hotmail.com wrote:

> > > Don't understand - can anyone shed light?
>
> > The compiler knows that ((int)MyVariable > 0) is always true.
>
> But it isn't! MyVariable can (and sometimes is) exactly 0.

That sounds like it's a compiler bug then. I know you've now got a
workaround, but could you post a short but complete example of the
original problem so we can investigate further? See
http://pobox.com/~skeet/csharp/complete.html for what I mean by that.

Jon

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Tom Spink - 22 Jun 2007 09:43 GMT

>> teddysn...@hotmail.com wrote:
>> > I'm new to C# - recent background mainly ASP.NET with VB.NET.
[quoted text clipped - 24 lines]
>
> Edward

Hi Edward,

What *is* MyVariable? Please could you provide a larger coding context?

Signature

Tom Spink
University of Edinburgh

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Unreachable expression code detected

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