Hi Joe Enos
I'm not so sure about the problem but....
when you use the operator ":", the left side (when the clausule is true)
and right (when it's false) has to have the same type
int myint = b ? 1 : 2;
Because exists the conversion because int is a well-known datatype in .net.
When you pass the name of two methods
Func<int> myFunc = b ? DoSomething : DoSomethingElse;
The compiler screams:
* there is no implicit conversion between 'method group' and 'method group'*
I think the compiler don't know exactly the type, so you have to inform to
the compiler explicitily
So see this
class Teste
{
public static int DoSomething() { return 1; }
public static int DoSomethingElse() { return 2; }
public static bool GetSomeBoolean(){return true;}
public static void Main(string[] args)
{
bool b = GetSomeBoolean();
Func<int> myFunc = b ? (Func<int>)DoSomething :
(Func<int>)DoSomethingElse;
System.Console.WriteLine(myFunc().ToString());
}
}
public delegate int Func<T>();
Compile ? yes
execute ? yes
So, I think the reason is that you have to inform to the compiler explicity
the type. Since delegate is a class, you can use a simple explicit cast
(Func<int>), ok ?
I am not so sure....but i think this is the way...
Best Regards
Does
On Thu, May 21, 2009 at 4:59 PM, Joe Enos <[email protected]> wrote:
>
> Kind of a weird issue here - not really a problem, but I'm hoping
> someone can explain it...
>
> Suppose I have a delegate variable and want to assign to it
> conditionally based on the value of a boolean. For example:
>
> public static int DoSomething() { return 1; }
> public static int DoSomethingElse() { return 2; }
>
> public static void Main(string[] args)
> {
> bool b = GetSomeBoolean();
>
> /* Method #1 - This does not work - gives me a compile-time error:
> error CS0173: Type of conditional expression cannot be determined
> because there is no implicit conversion between 'method group' and
> 'method group'
> */
> Func<int> myFunc = b ? DoSomething : DoSomethingElse;
>
> // the following three work fine
>
> /* Method #2 */
> Func<int> myFunc;
> if (b) myFunc = DoSomething; else myFunc = DoSomethingElse;
>
> /* Method #3 */
> Func<int> myFunc = b ? new Func<int>(DoSomething) :
> DoSomethingElse;
>
> /* Method #4 */
> Func<int> myFunc = b ? DoSomething : new Func<int>
> (DoSomethingElse);
> }
>
> Any ideas on why method #1 doesn't work? Obviously there are at least
> three other ways of writing this statement (#2,3,4), but I'm curious
> as to why #1 fails at compile time, and even more curious why 2, 3,
> and 4 work when 1 doesn't. #3 and #4 are identical to #1, except one
> method group is wrapped inside of a constructor for Func, which I
> thought was always optional.
>
> No big deal, but it's just bugging me...
>
> Thanks
>
> Joe
--
Paulo Alexandre Costa
Universidade Estadual do Ceará - UECE
Great-Ufc Desenvolvedor .Net
Linux User #464032
"A velocidade impressionante dos computadores é de utilidade limitada se os
programas que neles rodam usam algoritmos ineficientes."
