c# Optional parameters, named parameters

void M(int x=9,string s="a",DateTime dt = default(DateTime))
{...}

Main()
{
M();//Use default values
M(8,"b"): //Implicitly specify method parameters, no specified default value is used
M(6,"v",);//Same as above
M(6,dt:);//Explanatory specified parameter name, pass the value for the specified parameter
}