actual actual actual actual in C#

Printer Data Matrix 2d barcode in C# actual actual actual actual

When you use an invocation with separate actual parameters for a parameter array, the compiler does the following: Takes the list of actual parameters and uses them to create and initialize an array in the heap. Stores the reference to the array in the formal parameter on the stack. If there are no actual parameters at the position corresponding to the formal parameter array, the compiler creates an array with 0 elements and uses that. For example, the following code declares a method called ListInts, which takes a parameter array. Main declares three ints and passes them to the array. class MyClass Parameter array { public void ListInts( params int[] inVals ) { if (inVals != null) for (int i = 0; i < inVals.Length; i++) // Process the array. { inVals[i] = inVals[i] * 10; Console.WriteLine("{0} ", inVals[i]); // Display new value. } } } class Program { static void Main() { int first = 5, second = 6, third = 7;

MyClass mc = new MyClass(); mc.ListInts( first, second, third ); // Call the method. Actual parameters Console.WriteLine("{0}, {1}, {2}", first, second, third); } } This code produces the following output: 50 60 70 5, 6, 7

Figure 5-10 illustrates the following about the values of the actual and formal parameters at various stages in the execution of the method: Before the method call, the three actual parameters are already on the stack. By the beginning of the method, the three actual parameters have been used to initialize an array in the heap, and the reference to the array has been assigned to formal parameter InputList. Inside the method, the code first checks to make sure that the array reference is not null, and then processes the array by multiplying each element in the array by 10, and storing it back. After method execution, the formal parameter, InputList, is out of scope.

Figure 5-10. Parameter arrays An important thing to remember about parameter arrays is that when the array is created in the heap, the values of the actual parameters are copied to the array. In this way, they are like value parameters: If the array parameter is a value type, the values are copied, and the actual parameters cannot be affected inside the method. If the array parameter is a reference type, the references are copied, and the objects referenced by the actual parameters can be affected inside the method.

You can also create and populate an array before the method call, and pass the single array variable as the actual parameter. In this case, the compiler uses your array, rather than creating one. For example, the following code uses method ListInts, declared in the previous example. In this code, Main creates an array and uses the array variable as the actual parameter, rather than using separate integers. static void Main() { int[] MyArr = new int[] { 5, 6, 7 }; MyClass mc = new MyClass(); mc.ListInts(MyArr); foreach (int x in MyArr) Console.WriteLine("{0}", x); } This code produces the following output: 50 60 70

Since there are four parameter types, it is sometimes difficult to remember their various characteristics. Table 5-2 summarizes them, making it easier to compare and contrast them. Table 5-2. Summary of Parameter Type Syntactic Usage

The formal parameter aliases the actual parameter. The formal parameter aliases the actual parameter. This allows passing a variable number of actual parameters to a method.

So far, you know that local variables and parameters are kept on the stack. Let s look at that organization a little further. When a method is called, memory is allocated at the top of the stack, to hold a number of data items associated with the method. This chunk of memory is called the stack frame for the method. The stack frame contains memory to hold the following: The return address that is, where to resume execution when the method exits Those parameters that allocate memory, that is, the value parameters of the method, and the parameter array if there is one Various other administrative data items relevant to the method call When a method is called, its entire stack frame is pushed onto the stack. When the method exits, its entire stack frame is popped from the stack. Popping a stack frame is sometimes called unwinding the stack. For example, the following code declares three methods. Main calls MethodA, which calls MethodB, creating three stack frames. As the methods exit, the stack unwinds. class Program { static void MethodA( int par1, int par2) { Console.WriteLine("Enter MethodA: {0}, {1}", par1, par2); MethodB(11, 18); // Call MethodB. Console.WriteLine("Exit MethodA"); } static void MethodB(int par1, int par2) { Console.WriteLine("Enter MethodB: {0}, {1}", par1, par2); Console.WriteLine("Exit MethodB"); } static void Main( ) { Console.WriteLine("Enter Main"); MethodA( 15, 30); Console.WriteLine("Exit Main"); } }