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C# Conditional Statements |
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For branching statement execution we have 2 types of conditional statements in C#.
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An Example:
Lets discuss the if statement with an example. In the example below if the user has not entered anything for his name,
then the code in first if block is executed. To check if the user has entered his name we are using String.Empty
field.
This will determine if a string is empty.
If the user has enetered his name then the first if block is skipped. The control will not enter into the if block. The code in
second if
block will be executed.
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using
System;
class
IfElseDemo
{
public static
void Main()
{
Console.WriteLine("Please enter your name");
// This message will be printed to the screen to prompt the
user to enter their name
string Name = Console.ReadLine();
// Read the name into a Local Variable
if (Name == String.Empty)
// If Name is empty then execute code in if block
{
Console.WriteLine("You have
not entered your name");
}
if (Name != String.Empty)
// If Name variable is not empty then execute code in if
block
{
Console.WriteLine("Welcome
" + Name);
}
}
}
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The above example can also be written as shown below. Here we are using if..else
instead of 2 if statements. In the first example as we are using 2 if statements,
the if condition will be checked in both the if blocks, and when the condition evaluates
to a boolean true, the code in the respective if block is executed else, the code
will be skipped.
Here in the below example as we are using if..else, first the
if condition will be checked and if the condition evaluates to a boolean
true, then the code in if block is executed and the else block is skipped.
On the other hand when the condition
in the if block evaluates to a boolean
false, the code in if block is skipped and
the code in else block is executed. |
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using
System;
class
IfElseDemo
{
public
static void Main()
{
Console.WriteLine("Please enter your name");
string Name = Console.ReadLine();
if (Name == String.Empty)
{
Console.WriteLine("You have
not entered your name");
}
else
{
Console.WriteLine("Welcome
" + Name);
}
}
}
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A variation of if..else statement is shown in the below example. We have an
if
statement, followed by multiple else if statements and finally an else statement. This variation of if statement can
be used to check multiple conditions. |
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using
System;
class
IfElseDemo
{
public
static void Main()
{
Console.WriteLine("Enter any number between 1 and
30");
int Number = Convert.ToInt16(Console.ReadLine());
if (Number ==10)
{
Console.WriteLine("Entered
Number is 10");
}
else if (Number ==20)
{
Console.WriteLine("Entered
Number is 20");
}
else if (Number ==30)
{
Console.WriteLine("Entered
Number 30");
}
else
{
Console.WriteLine("Entered
Number is not 10,20 or 30");
}
}
}
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Another conditional statement in C# is the switch statement.
Switch statement is especially useful if you want to check for multiple
if conditions. To better understand
switch statements lets look at an example. We will rewrite the above example that
has multiple if statements
using a switch statement and lets dissect what's going
on
- To the switch statement we have passed our variable Number
of type int. Inside the switch code block we have series of
case blocks. The case keyword is followed by an integers value (10,20 etc).
- If the passed number variable has a value of 10 then, the statement in Case 10: block will be executed.
- At the end of each case statement we have a break
keyword. This keyword will break the execution and the control comes out of the loop. It is a compile time error in C# if you dont have the break
statement.
- Finally we have the default code block. This block will be executed only if none of the case blocks are executed. In our example if the passed in Number value is not 10,20 or 30 then non of case blocks will be executed and hence the default code block gets executed.
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using
System;
class
SwitchCase
{
public
static void Main()
{
Console.WriteLine("Enter any number between 1 and
30");
int Number = Convert.ToInt16(Console.ReadLine());
switch (Number)
{
case 10:
Console.WriteLine("Entered
Number is 10");
break;
case 20:
Console.WriteLine("Entered
Number is 20");
break;
case 30:
Console.WriteLine("Entered
Number is 20");
break;
default:
Console.WriteLine("Entered Number is not 10,20 or 30");
break;
}
}
}
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The above program can also be written as shown in the below example.
- In this example we have Case 10 and Case 20 labels without any code in them followed by Case 30.
- If the passed in Number value is 10,20 or 30 then the code in Case 30: block will be executed. This construct is especially useful when you want to check for multiple conditions and execute the same lines of code.
- By placing case statements together, with no code in-between, you create a single case for multiple values. A case without any code will automatically fall through to the next case.
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using
System;
class
CaseDemo
{
public
static void Main()
{
Console.WriteLine("Enter any number between 1 and
30");
int Number = Convert.ToInt16(Console.ReadLine());
switch (Number)
{
case 10:
case 20:
case 30:
Console.WriteLine("Entered
Number is {0}",Number);
break;
default:
Console.WriteLine("Entered
Number {0} is not 10,20 or 30",Number);
break;
}
}
}
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Another way to control the flow of logic in a switch statement is by using the
goto statement and Labels as shown in the below example.
- In this example we have 2 labels, Begin and Decide. Labels in a C# program are usually used to designate locations.
- When the program executes "Enter any number between 1 and 30" is displayed to the user.
- If the user has entered 10,20 or 30 then the code block following case 30: will be executed. The goto Decide: statement will cause the control to jump to the Decide: label and start executing from there again.
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using
System;
class
CaseDemo
{
public
static void Main()
{
Begin: //
This is a Label
Console.WriteLine("Enter any number between 1 and
30");
int Number = Convert.ToInt16(Console.ReadLine());
switch (Number)
{
case 10:
case 20:
case 30:
Console.WriteLine("Entered
Number is {0}", Number);
goto Decide;
default:
Console.WriteLine("Entered
Number {0} is not 10,20 or 30", Number);
goto Decide;
}
Decide:
//This is a Label
Console.WriteLine("Do you want to continue? Yes
or No");
string choice = Console.ReadLine();
switch (choice)
{
case "Yes":
case "Y":
case "y":
goto Begin;
case "No":
case "N":
case "n":
Console.WriteLine("Program
Terminated");
break;
default:
Console.WriteLine("Wrong
Choice");
goto Decide;
}
}
}
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Njoy Programming
ByPrasad Cherukuri
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