C# also supports the params modifier which allows a method to accept a variable number of parameters...

Odnośniki

Smutek to uczucie, jak gdyby się tonęło, jak gdyby grzebano cię w ziemi.
Search ROM [F0h] When a system is initially brought up, the bus master might not know the number of devices on the 1-Wire bus or their 64-bit ROM codes...
} page 252 Programming C# } Although in this example these two classes are very similar, in a production program any number of disparate classes...
Polecenie traceroute zwykle jest wykorzystywane w ten sposób, jak polecenie ping – jako parametr należy podać nazwę hosta docelowego...
The Arrays class has another sort( ) method that takes a single argument: an array of Object, but with no Comparator...
Every programming language enables some method for declaring local (or global) variables that can be used to store data...
Funkcja explain() jako parametr przyjmuje napis i używa go w metodzie document...
<method> <ejb−name>Product</ejb−name> <method−name>findByCategory</method−name>...
niespodziewanie zjawiała się stająca w poprzek prowadzonym staraniom burza, która niweczyła w istocie to, co rozum uznawał za doprowadzone do końca...
- Zaryzykujmy jeszcze raz - zaproponował Yarber, zanim pozostali zdążyli o tym pomyśleć...
31 S e u t e s byÂł naczelnikiem jednego z plemion Odrysów...

Smutek to uczucie, jak gdyby się tonęło, jak gdyby grzebano cię w ziemi.

The params keyword is discussed in Chapter 9.
4.5.1 Passing by Reference
Methods can return only a single value (though that value can be a collection of values). Let's return to the Time class and add a GetTime( ) method which returns the hour, minutes, and seconds.
Because we cannot return three values, perhaps we can pass in three parameters, let the method modify the parameters, and examine the result in the calling method. Example 4-7 shows a first attempt at this.
Example 4-7. Returning values in parameters
public class Time
{
// public accessor methods
public void DisplayCurrentTime( )
{
System.Console.WriteLine("{0}/{1}/{2} {3}:{4}:{5}",
Month, Date, Year, Hour, Minute, Second);
}

public int GetHour( )
{
return Hour;
}

public void GetTime(int h, int m, int s)
{
h = Hour;
m = Minute;
s = Second;
}

// constructor
public Time(System.DateTime dt)
{

page 73
Programming C#

Year = dt.Year;
Month = dt.Month;
Date = dt.Day;
Hour = dt.Hour;
Minute = dt.Minute;
Second = dt.Second;
}

// private member variables
private int Year;
private int Month;
private int Date;
private int Hour;
private int Minute;
private int Second;

}

public class Tester
{
static void Main( )
{
System.DateTime currentTime = System.DateTime.Now;
Time t = new Time(currentTime);
t.DisplayCurrentTime( );

int theHour = 0;
int theMinute = 0;
int theSecond = 0;
t.GetTime(theHour, theMinute, theSecond);
System.Console.WriteLine("Current time: {0}:{1}:{2}",
theHour, theMinute, theSecond);

}

}

Output:
11/17/2000 13:41:18
Current time: 0:0:0
Notice that the "Current time" in the output is 0:0:0. Clearly, this first attempt did not work. The problem is with the parameters. We pass in three integer parameters to GetTime( ), and we modify the parameters in GetTime( ), but when the values are accessed back in Main( ), they are unchanged. This is because integers are value types, and so are passed by value; a copy is made in GetTime( ). What we need is to pass these values by reference.
Two small changes are required. First, change the parameters of the GetTime method to indicate that the parameters are ref (reference) parameters:

public void GetTime(ref int h, ref int m, ref int s)
{
h = Hour;
m = Minute;
s = Second;
}
Second, modify the call to GetTime( ) to pass the arguments as references as well: page 74
Programming C#
t.GetTime(ref theHour, ref theMinute, ref theSecond);
If you leave out the second step of marking the arguments with the keyword ref, the compiler will complain that the argument cannot be converted from an int to a ref int.
The results now show the correct time. By declaring these parameters to be ref parameters, you instruct the compiler to pass them by reference. Instead of a copy being made, the parameter in GetTime( ) is a reference to the same variable (theHour) that is created in Main( ). When you change these values in GetTime( ), the change is reflected in Main( ).
Keep in mind that ref parameters are references to the actual original value—it is as if you said
"here, work on this one." Conversely, value parameters are copies—it is as if you said "here, work on one just like this."
4.5.2 Passing Out Parameters with Definite Assignment
C# imposes definite assignment , which requires that all variables be assigned a value before they are used. In Example 4-7, if you don't initialize theHour, theMinute, and theSecond before you pass them as parameters to GetTime( ), the compiler will complain. Yet the initialization that is done merely sets their values to 0 before they are passed to the method:
int theHour = 0;
int theMinute = 0;
int theSecond = 0;
t.GetTime( ref theHour, ref theMinute, ref theSecond);
It seems silly to initialize these values because you immediately pass them by reference into GetTime where they'll be changed, but if you don't, the following compiler errors are reported: Use of unassigned local variable 'theHour'
Use of unassigned local variable 'theMinute'
Use of unassigned local variable 'theSecond'
C# provides the out parameter modifier for this situation. The out modifier removes the requirement that a reference parameter be initiailzed. The parameters to GetTime( ), for example, provide no information to the method; they are simply a mechanism for getting information out of it. Thus, by marking all three as out parameters, you eliminate the need to initialize them outside the method. Within the called method the out parameters must be assigned a value before the method returns. Here are the altered parameter declarations for GetTime( ):
public void GetTime(out int h, out int m, out int s)
{
h = Hour;
m = Minute;
s = Second;
}
and here is the new invocation of the method in Main( ):
t.GetTime( out theHour, out theMinute, out theSecond);
To summarize, value types are passed into methods by value. Ref parameters are used to pass value types into a method by reference. This allows you to retrieve their modified value in the calling page 75
Programming C#
method. Out parameters are used only to return information from a method. Example 4-8 rewrites Example 4-7 to use all three.
Example 4-8. Using in, out, and ref parameters
public class Time
{
// public accessor methods
public void DisplayCurrentTime( )
{
System.Console.WriteLine("{0}/{1}/{2} {3}:{4}:{5}",
Month, Date, Year, Hour, Minute, Second);
}

public int GetHour( )
{
return Hour;
}

public void SetTime(int hr, out int min, ref int sec)