Statements in C#
Here we are going to discuss various statements available in C#. We discuss about if statement, switch statements in C#.
Empty statement:
;
; is a terminator, not a separator
Assignment Statement:
x = 2 * y + 1;
Calling the Method:
string s = "A, B, C";
string[] parts = s.Split(','); // invocation of an object method (non-static)
s = String.Join(" + ", parts); // invocation of a class method (static)
if statement:
Like any other language in C# also has if statement to check the condition.
if ('0' <= ch && ch <= '9')
{
val = ch - '0';
}
else if ('A' <= ch && ch <= 'Z')
{
val = 10 + ch - 'A';
}
else
{
val = 0;
Console.WriteLine("invalid character " + ch);
}
switch statement:
switch statement is used to handle multiple selections by passing control to one of the case statements within its body.
switch (country)
{
case "England":
case "Canada":
case "USA":
language = "English";
break;
case "Germany":
case "Austria":
case "Switzerland":
language = "German";
break;
case null:
Console.WriteLine("no country specified");
break;
default:
Console.WriteLine("don't know the language of " + country);
break;
}
Type of the switch expression:
integer type, char, enum or string (null ok as a case label).
No fall-through (unlike in C or in Java)!:
Every statement sequence in a case must be terminated with break (or return, goto, throw).
If no case label matches è default
If no default specified è continuation after the switch statement
switch with goto statement:
int state = 0;
int ch = Console.Read();
switch (state)
{
case 0:
if (ch == 'a')
{
ch = Console.Read();
goto case 1;
}
else if (ch == 'c') goto case 2;
else goto default;
case 1:
if (ch == 'b')
{
ch = Console.Read();
goto case 1;
}
else if (ch == 'c') goto case 2;
else goto default;
case 2:
Console.WriteLine("input valid");
break;
default:
Console.WriteLine("illegal character " + ch);
break;
}
While statement:
while (i < n)
{
sum += i;
i++;
}
do-while statement:
do
{
sum += a[i];
i--;
} while (i > 0);
for statement:
for (int i = 0; i < n; i++)
{
sum += i;
}
foreach statement:
For iterating over collections and arrays
int[] a = {3, 17, 4, 8, 2, 29};
foreach (int x in a)
sum += x;
string s = "Hello";
foreach (char ch in s)
Console.WriteLine(ch);
Queue q = new Queue(); // elements are of type object
q.Enqueue("John"); q.Enqueue("Alice");
foreach (string s in q)
Console.WriteLine(s);
break statement:
For exiting a loop or a switch statement. There is no break with a label like in Java (use goto instead).
continue statement:
Continues with the next loop iteration.
return statement:
Returning from a void method
void Foo (int x) {
if (x == 0) return;
...
}
Returning a value from a function method
int Max (int a, int b) {
if (a > b) return a; else return b;
}
class C {
static int Main() {
...
return errorCode; // The Main method can be declared as a function;
} // the returned error code can be checked with the
// system variable errorlevel
}
Getting input from Keyboard :
int ch = Console.Read();
returns the next character.
waits until the user pressed the return key.
e.g. input: "abc" + return key.
Read returns: 'a', 'b', 'c', '\r', '\n'.
after the last character (Ctrl-Z + return) Read returns -1
string line = Console.ReadLine();
returns the next line (after Ctrl-Z+CR+LF it returns null).
waits until the user pressed the return key.
returns the line without CR, LF.
Input from a File:
using System;
using System.IO;
class FileInput
{
static void Main() {
FileStream s = new FileStream("input.txt", FileMode.Open);
StreamReader r = new StreamReader(s);
string line = r.ReadLine();
while (line != null) {
...
line = r.ReadLine();
}
r.Close();
}
}
It is not possible to have multiple StreamReaders working on the same streamat the same time.
Reading Command-line Parameters:
using System;
class CmdInput
{
static void Main(string[] arg)
{ // e.g. invoked as: Test value = 3
for (int i = 0; i < arg.Length; i++)
Console.WriteLine("{0}: {1}", i, arg[i]); // output (tokens are separated by blanks):
// 0: value
// 1: =
// 2: 3
foreach (string s in arg)
Console.WriteLine(s); // output:
}
}
