1. C# — Console Application
1. Create a Console Project
2. The “Hello World” program
3. Standard Input & Output
4. Arrays
5. Call By Value & Call By Reference
6. The foreach statement

2. 1. Create a Console Project
Open MS Visual Studio .NET 2003
Then click on the New Project button

3. Do the following to create the project

4. The following program has been created
using System;
namespace ConsoleApplication {
/// <summary>
/// Summary description for Class1.
/// </summary>
class Class1
/// The main entry point for
/// the application.
[STAThread]

5. static void Main(string[] args){ //
// TODO: Add code to start
// application here }
Build Solution: to compile the program.
Start or Start without Debugging: to run the program.
There is no output if we run the program now.

6. We should replace Class1 with a user-friendly name

7. 2. The Hello World Program
We add the following code for our first program:
static void Main(string[] args) { //
// TODO: Add code to start
// application here
Console.WriteLine(
"Hello World"); }
Run
Hello World
Press any key to continue

8. 3. Standard Input & Output
Output: We have used the WriteLine() method to output “Hello World” in our first program.
We can use the Write() method as follows
Console.Write("Hello ");
Console.WriteLine("World"); or
Console.WriteLine("Hello World");
Console.Write("\n");

9. More examples:
Example 1:
Console.WriteLine("PGUI " );
Example 2:
int year = 2004;
Console.WriteLine("PGUI " + year);
PGUI 2004
Example 3:
double x = 55.77;
Console.WriteLine("x = " + x);
x = 55.77

10. Example 4:
char c = 'x'; double d = 0.5;
Console.WriteLine(c + " = " + d);
x = 0.5
Example 5:
string s = "Hello World";
Console.WriteLine(s);
Hello World

11. Example 6:
int x = 2004; double y = 0.5;
Console.WriteLine("{0} {1}", x, y);
Example 7:
double y = 7.5;
Console.WriteLine("{0, 10:C5}", y);
currency
10 places
5 decimal places $

12. Input: the Read() method
Example:
int i;
Console.WriteLine("Enter string:");
while ((i = Console.Read()) != -1) Console.WriteLine(
(char)i + ": " + i);
The Read() method reads the next character from the standard input stream and returns its American Standard Code

13. Enter string: az
a: 97
z: 122
: 13
:10 ^Z
Press any key to continue
a: 97, ..., z: 122
carriage return: 13
newline: 10

14. The ReadLine() method
Example 1:
double price; string inputString;
Console.Write("Enter price: ");
inputString = Console.ReadLine();
price = double.Parse(inputString );
Console.Write("price = ");
Console.WriteLine("{0:C}", price);
Enter price: 55
price = $55.00
Press any key to continue

15. Example 2:
int ID;
string inputString;
Console.Write("Enter your ID: ");
inputString = Console.ReadLine();
ID = int.Parse(inputString );
Console.Write("Your ID is: ");
Console.WriteLine(ID);
Enter your ID:
Your ID is:
Press any key to continue

16. Simple native types:
bool, int, double, char, byte
Integral simple types:
short, int, long, ushort, uint, ulong,
Floating-point simple types:
float, double, decimal
16 bytes
Fixed precision up to 28 or 29 digits

17. 4. Arrays Example 1: one-dimensional array int[] day = new int[2];
We can declare and initialise as follows
int[] day = new int[2] {23, 24}; or
int[] day = {23, 24};

18. Example 2: use array as an argument of a user-defined method
using System;
namespace ConsoleApplication {
class Welcome
static void Main(string[] args)
int[] a = {3, 5};
int sum = sumArray(a);
Console.WriteLine(sum); }

19. // Implementation of the
// sumArray() method
static int sumArray(int[] arr) {
int sum = 0;
int i;
for (i=0; i<arr.Length; i++)
sum += a[i];
return sum; }
} // end class Welcome
} // end namespace 8
Press any key to continue

20. Example 3: multi-dimensional array
int[] day; // 1D array
double[,] matrix; // 2D array
double[,,] plane; // 3D array
int[,] data = new int[3,5];
int[,] a = {{1,2}, {3,4}, {5,6}};
int[,] b = {{1,2,3}, {4,5,6}};
int[,] c = {{1,2,3,4,5,6}};

21. Example 4:
class Welcome {
public static void Main()
int[,] data = new int[3,5]; // 3 rows 5 columns
Console.WriteLine(
"Number of elements = " +
data.Length);
for (int i = 0;
i < data.GetLength(0);
i++)

22. {
Console.WriteLine(
"Row " + i + ": ");
for (int j = 0;
j < data.GetLength(1);
j++)
data[i,j] = i * j;
Console.Write(
data[i,j] + ", "); }
Console.WriteLine();

23. Number of Elements = 15
Row 0: 0, 0, 0, 0, 0,
Row 1: 0, 1, 2, 3, 4,
Row 2: 0, 2, 4, 6, 8,
Press any key to continue

24. 5. Call By Value & Call By Reference
Example 1: Call By Value
class FailedSwap {
public static void Main()
int numOne = 1, numTwo = 2;
Swap(numOne, numTwo);
Console.WriteLine(
"numOne = " + numOne);
"numTwo = " + numTwo); }

25. public static void
Swap(int x, int y) {
int temp;
temp = x;
x = y;
y = temp; }
numOne = 1
numTwo = 2
Press any key to continue

26. Example 2: Call By Reference
class SwapTwo {
public static void Main()
int numOne = 1, numTwo = 2;
Swap(ref numOne, ref numTwo);
Console.WriteLine(
"numOne = " + numOne);
"numTwo = " + numTwo); }

27. public static void
Swap(ref int x, ref int y) {
int temp;
temp = x;
x = y;
y = temp; }
numOne = 2
numTwo = 1
Press any key to continue

28. 6. The foreach statement foreach(type variableName in arrayName)
do_statement
Example 1:
static void WriteArray(int[] a) {
foreach(int element in a)
Console.Write(element + " "); }