Recently I've came across a strange behavior that took me some thinking to work around.
As you may know, my language of choice has been VB for as long as I can remember. However, I, like any good developer, can work just as good in C#. Really, it's no biggie.
Anyway, what I'm talking about here is
dynamic type resolution.
For instance let's say we have the following VB program:
Module Program
Sub Main()
Dim value As Object = 123
Format(123)
Format(value)
End Sub
Sub Format(ByVal value As IFormattable)
Console.WriteLine(value.ToString(Nothing, Nothing))
End Sub
End Module
When ran, the above program will generate the following output:
123
123
Easy enough, huh?
Now, if we port this program to C# like this:
class Program
{
static void Main(string[] args)
{
object value = 123;
Format(123);
Format(value);
}
static void Format(IFormattable value)
{
Console.WriteLine(value.ToString(null, null));
}
}
Which is the literal translation of the VB program above, we can't even compile to program, because the C# compiler gives the following errors:
error CS1502: The best overloaded method match for 'DynamicCS.Formatter.Format(System.IFormattable)' has some invalid arguments
error CS1503: Argument '1': cannot convert from 'object' to 'System.IFormattable'
It's the same damn code, how come C# can't convert from object to IFormattable?
Well, the answer is that the C# compiler requires that all types to be known at compile time, rater than establish at runtime.
