10.1 Application startup
Application startup occurs when the execution environment calls a designated
method, which is referred to
as the application’s entry point. This entry point method is always named
Main, and shall have one of the
following signatures:
static void Main() {.}
static void Main(string[] args) {.}
static int Main() {.}
static int Main(string[] args) {.}
As shown, the entry point may optionally return an int value. This return
value is used in application
termination (§10.2).
The entry point may optionally have one formal parameter, and this formal
parameter may have any name. If
such a parameter is declared, it must obey the following constraints:
. The implementation shall ensure that the value of this parameter is not
null.
. Let args be the name of the parameter. If the length of the array
designated by args is greater than
zero, the array members args[0] through args[args.Length-1], inclusive,
must refer to strings,
called application parameters, which are given implementation-defined
values by the host environment
prior to application startup. The intent is to supply to the application
information determined prior to
application startup from elsewhere in the hosted environment. If the host
environment is not capable of
supplying strings with letters in both uppercase and lowercase, the
implementation shall ensure that the
strings are received in lowercase. [Note: On systems supporting a command
line, application parameters
correspond to what are generally known as command-line arguments. end note]
Since C# supports method overloading, a class or struct may contain
multiple definitions of some method,
provided each has a different signature. However, within a single program,
no class or struct shall contain
more than one method called Main whose definition qualifies it to be used
as an application entry point.
Other overloaded versions of Main are permitted, however, provided they
have more than one parameter, or
their only parameter is other than type string[].
An application can be made up of multiple classes or structs. It is
possible for more than one of these classes
or structs to contain a method called Main whose definition qualifies it to
be used as an application entry
point. In such cases, one of these Main methods must be chosen as the entry
point so that application startup
can occur. This choice of an entry point is beyond the scope of this
specification.no mechanism for
specifying or determining an entry point is provided.
In C#, every method must be defined as a member of a class or struct.
Ordinarily, the declared accessibility
(§10.5.1) of a method is determined by the access modifiers (§17.2.3)
specified in its declaration, and
similarly the declared accessibility of a type is determined by the access
modifiers specified in its
declaration. In order for a given method of a given type to be callable,
both the type and the member must be
accessible. However, the application entry point is a special case.
Specifically, the execution environment
can access the application’s entry point regardless of its declared
accessibility and regardless of the declared
accessibility of its enclosing type declarations.
In all other respects, entry point methods behave like those that are not
entry points.
