Unreachable expression code detected

[teddysnips]

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

 

[Marc Gravell]

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

 

[Peter Bradley]

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

 

[Alun Harford]

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?

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

Alun Harford

 

[teddysnips]

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

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

Edward

 

[teddysnips]

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;

Doh! That's much more elegant. Thanks.

Edward

 

[Jon Skeet [C# MVP]]

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

 

[Tom Spink]

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

Edward

Hi Edward,

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

 

[Peter Bradley]

Ysgrifennodd (e-mail address removed):

Doh! That's much more elegant. Thanks.

Edward

The pleasure's mine


Peter