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if, else if, else Statements in C#

if statement is the single most important statements in every programming language eg c, c++, c#, F#, javascript etc . Being able to set up conditional blocks of code is a fundamental principal of writing software.If condition is the very simple to us. The if statement needs a boolean result, that is, true ( or false as boolen value.


C# Conditions and If Statements

  • Less than: a < b
  • Less than or equal to: a <= b
  • Greater than: a > b
  • Greater than or equal to: a >= b
  • Equal to a == b
  • Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

C# has the following conditional statements:

  •  Use if to specify a block of code to be executed, if a specified condition is true
  •  Use else to specify a block of code to be executed, if the same condition is false
  •  Use else if to specify a new condition to test, if the first condition is false
  •  Use switch to specify many alternative blocks of code to be executed

If Statement

 We use the if statement to specify a block of C# code which is to be executed if a condition is True.

Syntax

if (condition)
{
  // block of code to be executed if the condition is true
}

Note: if is in lowercase letters, uppercase letters (If or IF) will generate an error.

Example
if (15 > 10)
{
     Console.WriteLine {“ 15 is greater than 10”);
}

We can also test variables:

int  x  = 15;
int y = 10;
if (x > y)
{
    Console.WriteLine(“x is greater than y “);
}
Example explained

In the example above we use two variables, x and y, to test whether x is greater than y (using the > operator). As x is 15, and y is 10, and we know that 15 is greater than 10, we print to the screen that "x is greater than y".


The else Statement

It is used to specify a block of code to be executed if the condition is False.

Syntax

if (condition)
{
  // block of code to be executed if the condition is true
}
else
{
    // block of code to be executed if the condition is false
}
Example
int  time = 20;
if ( time < 18) {
     Console.WriteLine (“ Good day.”);
} else
{
     Console.WriteLine (“Good evening.”);
}

 // Outputs “Good evening.”________________________________________

Example explained

In the example above, time (20) is greater than 18, so the condition is False. Because of this, we move on to the else condition and print to the screen "Good evening". If the time was less than 18, the program would print "Good day".


The else if Statement

 The else if statement is used to specify a new condition if the first condition is False.

Syntax
if (condition 1)
{
  // block of code to be executed if the condition 1 is true
}
else if ( condition 2)
{
    // block of code to be executed if the condition 1 is false and condition 2 is true
}
else ( condition 3)
{
    // block of code to be executed if the condition 1 is false and condition 2 is false
}
Example
int  time = 25;
if ( time < 10)
{
    Console.WriteLine(“Good morning.”);
} else if ( time < 20)
{       Console.WriteLine( “ Good day.”);
} else
{
      Console.WriteLine (“ Good evening.”);
}

// Outputs Good evening.

Example explained

In the example above, time (25) is greater than 10, so the first condition is False. The next condition, in the else if statement, is also False, so we move on to the else condition since condition1 and condition2 is both False - and print to the screen "Good evening".

 However, if the time was 14, our program would print "Good day."