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C# Conditions and If Statements
C# supports the usual logical conditions from mathematics:
- 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 in 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
The if Statement
Use the statement if to specify a C # code block to be used if the condition is true.
Syntax
if (condition)
{
// block of code to be executed if the condition is True
}
In the example below, we examine two values to determine if 20 is greater than 18. If the situation is true, print some text:
Example
if (20 > 18)
{
Console.WriteLine("20 is greater than 18");
}
We can also check the variables:
Example
int x = 20;
int y = 18;
if (x > y)
{
Console.WriteLine("x is greater than y");
}
The else Statement
Use else statement to specify a code block to use 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."
The else if Statement
Use the else if statement to specify a new condition if the first condition is False.
Syntax
if (condition1)
{
// block of code to be executed if condition1 is True
}
else if (condition2)
{
// block of code to be executed if the condition1 is false and condition2 is True
}
else
{
// block of code to be executed if the condition1 is false and condition2 is False
}
Example
int time = 22;
if (time < 10)
{
Console.WriteLine("Good morning.");
}
else if (time < 20)
{
Console.WriteLine("Good day.");
}
else
{
Console.WriteLine("Good evening.");
}
// Outputs "Good evening."
Short Hand If...Else (Ternary Operator)
There is also a short-hand alternative, known as a ternary operator because it contains three operands. It can be used instead of multiple lines of code in one line. It is often used for a simple replacement if other statements: There is also a short hand if not, known as a ternary operator because it consists of three operands. It can be used instead of multiple lines of code in one line. It is often used for a simple replacement if other statements:
Syntax
variable = (condition) ? expressionTrue : expressionFalse;
Instead of writing:
Example
int time = 20;
if (time < 18)
{
Console.WriteLine("Good day.");
}
else
{
Console.WriteLine("Good evening.");
}
You can simply write:
Example
int time = 20;
string result = (time < 18) ? "Good day." : "Good evening.";
Console.WriteLine(result);