Needing to cast from an interface to a concrete type indicates that something is wrong with the abstractions in use, likely that
something is missing from the interface. Instead of casting to a discrete type, the missing functionality should be added to the
interface. Otherwise there is a risk of runtime exceptions.
Noncompliant code example
public interface IMyInterface
{
void DoStuff();
}
public class MyClass1 : IMyInterface
{
public int Data { get { return new Random().Next(); } }
public void DoStuff()
{
// TODO...
}
}
public static class DowncastExampleProgram
{
static void EntryPoint(IMyInterface interfaceRef)
{
MyClass1 class1 = (MyClass1)interfaceRef; // Noncompliant
int privateData = class1.Data;
class1 = interfaceRef as MyClass1; // Noncompliant
if (class1 != null)
{
// ...
}
}
}
Exceptions
Casting to object doesn’t raise an issue, because it can never fail.
static void EntryPoint(IMyInterface interfaceRef)
{
var o = (object)interfaceRef;
...
}
