Datasheet

Book VIII
Chapter 1
Programming
Dynamically!
775
Putting Dynamic to Use
✦ int newString = (int) dynamicVariable;: This is an explicit
cast to int. The compiler encodes this as a cast — you actually change
the type here.
✦ Console.WriteLine(dynamicVariable);: Because there is no over-
load of WriteLine that accepts a dynamic type explicitly, the entire
method call is dispatched dynamically.
Making static operations dynamic
If the compiler chooses to make a static operation dynamic — as it did in
item 6 in the preceding section — the compiler rebuilds the code on the fly
to have it handle the dynamic variable. What does that mean for you? Glad
you asked.
Let’s take item 6, Console.WriteLine(dynamicVariable);. This piece
of code forces the compiler to build intermediary code, which checks for the
type of variable at runtime in order to come up with something that is writ-
able to the console. The compiled code first checks if the input is a static
type that it knows. Next, it checks for a type present in the program. Then
it will just try a few things that might work. It will fail with an error if it finds
nothing.
If this must happen, that’s fine. But remember that it is slower than all
git out. This is why Variant got such a bad rap in Visual Basic classic.
Dynamic is something you don’t use until you need it. It puts a tremendous
strain on the machine running the program, especially if all variables are
dynamic.
Understanding what’s happening under the covers
Let’s take an example right out of MSDN. Microsoft points out this simple
method:
class C
{
public dynamic MyMethod(dynamic d)
{
return d.Foo();
}
}
This is pretty straightforward stuff — a method that accepts a dynamic class
and returns the results of the type’s Foo method. Not a big deal.
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