Csharp/CSharp Tutorial/Class/Method Parameter
Содержание
- 1 A member function with two arguments
- 2 C# Parameter Modifiers
- 3 Creating a method with a reference argument.
- 4 How Arguments Are Passed
- 5 Method parameter hides the class member field
- 6 Parameter modifiers
- 7 params int[] args
- 8 Pass integer by ref
- 9 Pass integer value by value
- 10 Pass int value to a function
- 11 Pass int without "out" and "ref"
- 12 ref parameters
- 13 Use a parameter in a member function
- 14 use of "outer variable" in anonymous method
- 15 Use out for int type
- 16 Variable arguments to a method in C#.
A member function with two arguments
using System;
class ChkNum {
public int sum(int a, int b) {
int max;
max = a < b ? a : b;
return max;
}
}
class MainClass {
public static void Main() {
ChkNum ob = new ChkNum();
int a, b;
a = 7;
b = 8;
Console.WriteLine(ob.sum(a, b));
a = 100;
b = 8;
Console.WriteLine(ob.sum(a, b));
a = 100;
b = 75;
Console.WriteLine(ob.sum(a, b));
}
}7 8 75
C# Parameter Modifiers
Parameter Modifier Meaning in Life
(none) Assumed to be passed by value.
out Output parameters are assigned.
params send in a variable number of arguments as a single logical parameter.
ref The value is initially assigned by the caller, and may be optionally reassigned by the called method.Creating a method with a reference argument.
using System;
class MainClass {
static void Main() {
int x = 10;
Console.WriteLine("Before calling non-ref function, x = {0}", x);
NonRefFunction(x);
Console.WriteLine("After calling non-ref function, x = {0}", x);
RefFunction(ref x);
Console.WriteLine("After calling ref function, x = {0}", x);
}
static void NonRefFunction(int x) {
Console.WriteLine("Top of NonRefFunction. X = {0}", x);
x = x + 10;
Console.WriteLine("Bottom of NonRefFunction. X = {0}", x);
}
static void RefFunction(ref int x) {
Console.WriteLine("Top of RefFunction. X = {0}", x);
x = x + 10;
Console.WriteLine("Bottom of RefFunction. X = {0}", x);
}
}How Arguments Are Passed
Call-by-value:
- Copy the value of an argument into the formal parameter.
- Change made to the parameter have no effect on the argument used in the call .
Call-by-reference.
- A reference to an argument is passed to the parameter.
- Change made to the parameter will affect the argument used to call the subroutine.
When you pass a value type, such as int or double, to a method, it is passed by value.
An object is passed by reference
7.6.Method Parameter 7.6.1. How Arguments Are Passed 7.6.2. <A href="/Tutorial/CSharp/0140__Class/Parametermodifiers.htm">Parameter modifiers</a> 7.6.3. <A href="/Tutorial/CSharp/0140__Class/Passintvaluetoafunction.htm">Pass int value to a function</a> 7.6.4. <A href="/Tutorial/CSharp/0140__Class/Useaparameterinamemberfunction.htm">Use a parameter in a member function</a> 7.6.5. <A href="/Tutorial/CSharp/0140__Class/Amemberfunctionwithtwoarguments.htm">A member function with two arguments</a> 7.6.6. <A href="/Tutorial/CSharp/0140__Class/Passintwithoutoutandref.htm">Pass int without "out" and "ref"</a> 7.6.7. <A href="/Tutorial/CSharp/0140__Class/Passintegerbyref.htm">Pass integer by ref</a> 7.6.8. <A href="/Tutorial/CSharp/0140__Class/refparameters.htm">ref parameters</a> 7.6.9. <A href="/Tutorial/CSharp/0140__Class/Passintegervaluebyvalue.htm">Pass integer value by value</a> 7.6.10. <A href="/Tutorial/CSharp/0140__Class/paramsintargs.htm">params int[] args</a> 7.6.11. <A href="/Tutorial/CSharp/0140__Class/Useoutforinttype.htm">Use out for int type</a> 7.6.12. <A href="/Tutorial/CSharp/0140__Class/Creatingamethodwithareferenceargument.htm">Creating a method with a reference argument.</a> 7.6.13. <A href="/Tutorial/CSharp/0140__Class/VariableargumentstoamethodinC.htm">Variable arguments to a method in C#.</a> 7.6.14. <A href="/Tutorial/CSharp/0140__Class/Methodparameterhidestheclassmemberfield.htm">Method parameter hides the class member field</a> 7.6.15. <A href="/Tutorial/CSharp/0140__Class/CParameterModifiers.htm">C# Parameter Modifiers</a> 7.6.16. <A href="/Tutorial/CSharp/0140__Class/useofoutervariableinanonymousmethod.htm">use of "outer variable" in anonymous method</a>
Method parameter hides the class member field
public class Product {
public int yearBuilt;
public double maximumSpeed;
public int Age(int currentYear) {
int maximumSpeed = 100; // hides the field
System.Console.WriteLine("In Age(): maximumSpeed = " + maximumSpeed);
int age = currentYear - yearBuilt;
return age;
}
public double Distance(double initialSpeed, double time) {
System.Console.WriteLine("In Distance(): maximumSpeed = " + maximumSpeed);
return (initialSpeed + maximumSpeed) / 2 * time;
}
}
class MainClass{
public static void Main() {
Product redPorsche = new Product();
redPorsche.yearBuilt = 2000;
redPorsche.maximumSpeed = 150;
int age = redPorsche.Age(2001);
System.Console.WriteLine("redPorsche is " + age + " year old.");
System.Console.WriteLine("redPorsche travels " + redPorsche.Distance(31, .25) + " miles.");
}
}Parameter modifiers
Parameter modifier Passed by Variable must be definitely assigned
None Value Going in
ref Reference Going in
out Reference Going outparams int[] args
using System;
class MainClass
{
static void Main(string[] args)
{
MyMethod(5,5,5,5);
}
static public void MyMethod(params int[] args)
{
for (int I = 0; I < args.Length; I++)
Console.WriteLine(args[I]);
}
}5 5 5 5
Pass integer by ref
using System;
class MainClass
{
static void Main(string[] args)
{
int MyInt = 5;
MyMethodRef(ref MyInt);
Console.WriteLine(MyInt);
}
static public int MyMethodRef(ref int myInt)
{
myInt = myInt + myInt;
return myInt;
}
}10
Pass integer value by value
using System;
class MainClass
{
static void Main(string[] args)
{
int MyInt = 5;
MyMethod( MyInt);
Console.WriteLine(MyInt);
}
static public int MyMethod( int myInt)
{
myInt = myInt + myInt;
return myInt;
}
}5
Pass int value to a function
using System;
class MainClass
{
public static void Main() {
int SomeInt = 6;
int s = Sum(5, SomeInt);
Console.WriteLine(s);
}
public static int Sum(int x, int y) // Declare the method.
{
return x + y; // Return the sum.
}
}11
Pass int without "out" and "ref"
using System;
class MyClass
{
public int Val = 20;
}
class MainClass
{
static void MyMethod(MyClass myObject, int intValue)
{
myObject.Val = myObject.Val + 5;
intValue = intValue + 5;
}
static void Main()
{
MyClass myObject = new MyClass();
int intValue = 10;
Console.WriteLine("Before -- myObject.Val: {0}, intValue: {1}", myObject.Val, intValue);
MyMethod(myObject, intValue);
Console.WriteLine("After -- myObject.Val: {0}, intValue: {1}", myObject.Val, intValue);
}
}Before -- myObject.Val: 20, intValue: 10 After -- myObject.Val: 25, intValue: 10
ref parameters
using System;
class Color {
public Color() {
this.red = 0;
this.green = 127;
this.blue = 255;
}
protected int red;
protected int green;
protected int blue;
public void GetRGB(
ref int red, ref int green, ref int blue) {
red = this.red;
green = this.green;
blue = this.blue;
}
}
class Class1 {
static void Main(string[] args) {
Color c = new Color();
int red = 1;
int green = 2;
int blue = 3;
c.GetRGB(ref red, ref green, ref blue);
Console.WriteLine("R={0}, G={1}, B={2}", red, green, blue);
}
}Use a parameter in a member function
using System;
class ChkNum {
// Return true if x is prime.
public bool isPrime(int x) {
for(int i=2; i <= x/i; i++)
if((x %i) == 0) return false;
return true;
}
}
class MainClass {
public static void Main() {
ChkNum ob = new ChkNum();
for(int i=1; i < 10; i++)
if(ob.isPrime(i)) Console.WriteLine(i + " is prime.");
else Console.WriteLine(i + " is not prime.");
}
}1 is prime. 2 is prime. 3 is prime. 4 is not prime. 5 is prime. 6 is not prime. 7 is prime. 8 is not prime. 9 is not prime.
use of "outer variable" in anonymous method
using System;
using System.Collections.Generic;
using System.Text;
class Program
{
delegate void MessagePrintDelegate(string msg);
static void Main(string[] args)
{
string source = "Outer";
MessagePrintDelegate mpd3 = delegate(string msg)
{
Console.WriteLine("[{0}] {1}", source, msg);
};
LongRunningMethod(mpd3);
}
static void LongRunningMethod(MessagePrintDelegate mpd)
{
for (int i = 0; i < 99; i++)
{
if (i % 25 == 0)
{
mpd(string.Format("Progress Made. {0}% complete.", i));
}
}
}
static void PrintMessage(string msg)
{
Console.WriteLine("[PrintMessage] {0}", msg);
}
}Use out for int type
using System;
class MyClass
{
public int Val = 20;
}
class MainClass
{
static void MyMethod(out MyClass f1, out int f2)
{
f1 = new MyClass();
f1.Val = 25;
f2 = 15;
}
static void Main()
{
MyClass myObject = null;
int intValue;
MyMethod(out myObject, out intValue);
Console.WriteLine("After -- myObject.Val: {0}, intValue: {1}", myObject.Val, intValue);
}
}After -- myObject.Val: 25, intValue: 15
Variable arguments to a method in C#.
using System;
class MainClass {
public static void PrintParams(params object[] list) {
for (int i = 0; i < list.Length; ++i)
Console.WriteLine("Object {0} = {1} ({2})", i, list[i], list[i].GetType());
}
public static void Main() {
PrintParams(1, 2, "a", "b", 23.4);
}
}