Functions
In B#, functions are defined using the fn keyword. They have a return type, parameters and a body that can be executed. For example:
fn int add(int a, int b) return a+b;
Default parameters
Parameters can have default values: they must be the last ones, because they are optional. They are used this way:
fn int add(int a, int b=4) return a+b;
External functions
If you declare a function with extrn fn, the function will be defined at linking time.
extrn fn int add(int a, int b);