C# Language Specification

Binding-time

Static binding takes place at compile-time, whereas dynamic binding takes place at run-time. In the following sections, the term binding-time refers to either compile-time or run-time, depending on when the binding takes place.

The following example illustrates the notions of static and dynamic binding and of binding-time:

object o = 5;
dynamic d = 5;

Console.WriteLine(5); // static binding to Console.WriteLine(int)

Console.WriteLine(o); // static binding to Console.WriteLine(object)
Console.WriteLine(d); // dynamic binding to Console.WriteLine(int)

The first two calls are statically bound: the overload of Console.WriteLine is picked based on the compile-time type of their argument. Thus, the binding-time is compile-time.

The third call is dynamically bound: the overload of Console.WriteLine is picked based on the run-time type of its argument. This happens because the argument is a dynamic expression – its compile-time type is dynamic. Thus, the binding-time for the third call is run-time.

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