about casting

[Cor Ligthert [MVP]]

Your answer



Last reply Jon, feel free to make a last, but I won't reply in this thread
anymore.

Cor

 

[Scott M.]

(string) X, is in my ide more or less the same like CType(X,string)

while I see
X as string, the same as DirectCast(X, string)

I would interpret that in reverse:

I would think (string) x is more equivelent to DirectCast(x, String)

and

x as string is more like CType(x, String)

-Scott

 

[Jon Skeet [C# MVP]]

I would interpret that in reverse:

I would think (string) x is more equivelent to DirectCast(x, String)

and

x as string is more like CType(x, String)

But that's still wrong:
1) A cast expression in C# does more than DirectCast in VB (but less
than CType, I think)
2) x as string will never throw an exception, whereas CType can.

As I've said before, "as" is the same as TryCast as far as I can tell.

Jon

 

[Scott M.]

Yes, I get that Jon, but I'm not really thinking about exceptions here since
in VB, both DirectCast and CType can throw exceptions. I'm really talking
more in terms of performance when the cast is possible.

 

[Jon Skeet [C# MVP]]

Yes, I get that Jon, but I'm not really thinking about exceptions here since
in VB, both DirectCast and CType can throw exceptions. I'm really talking
more in terms of performance when the cast is possible.

If the cast is possible as an "inheritance-style" cast, both "as" and
direct casting are like DirectCast.

If a user-defined operator conversion is involved then direct casting
acts more like CType - but that's pretty rare, and the operator to call
is still decided at compile time.

I get the impression that CType is capable of deciding which conversion
to apply (like parsing a string to an integer) at exection time. That's
not the case with either direct casting or "as" in C#.