• Differentiate between the types of conditional statements.
• Recall the syntax for creating a conditional statement.
• Apply conditional statements to decision making in app logic.

There are times where we might want our programs to behave differently depending on the input received. In this case, C# provides the option of preparing in-advance decision making so that after a pre-established condition is met, the program will execute a specific section of code. These statements are referred to as conditional statements.

There are four conditional statements:

• if statement
• if/else statement
• else/if statement
• switch statement

Conditional statements can be used in conjunction with the following logical conditions:

• 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 != 5

The if statement is used when we require a specific condition to be met in order for a command to be executed. The code is executed if the condition is true.

The following is the syntax to create an if statement:

if (condition)
{
    //code that runs if condition is true
}

Provided below is an example of an if-statement that executes a string if the value 10 is greater than 3).

if (10 > 3)
{
    Console.WriteLine("10 is greater than 3.");
}

An if/else statement is used when after a specific condition fails, we want to make sure a specific command is executed.

The following is the syntax to create an if/else statement:

if(condition)
{
    //code that runs if condition is met
}
else
{
    //code that runs if condition is not met
}

Provided below is an example of an if/else statement that evaluates whether 4 x 5 is equal to 30. Given that 4 x 5 is equal to 20, the code executes the string within the else statement.

if(4 x 5 == 30)
{
    Console.WriteLine("The product of 4 x 5 is 30.")
}
else
{
    Console.WriteLine("The product of 4 x 5 is 20.")
}

An if/else statement is used when there is a need to test multiple conditions after the first condition fails. An if/else statement executes in the order of else/if statements until the final else statement executes.

The following is the syntax to create an else/if statement:

if (first condition)
{
    //code that runs if first condition is met
}
else if (second condition)
{
    //code that runs if second condition is met
}
else if (n condition)
{
    //code that runs if n condition is met
}
else
{
    //code that runs if none of the above conditions are met
}

Provided below is an example of an else/if statement that evaluates whether a person's testScore equates to either an A, B, C, D, or F letter grade.

int testScore = 74;

if (testScore >= 90)
{
    Console.WriteLine("A");
}
else if (testScore >= 80)
{
    Console.WriteLine("B");
}
else if (testScore >= 70)
{
    Console.WriteLine("C");
}
else if (testScore >= 60)
{
    Console.WriteLine("D");
}
else
{
    Console.WriteLine("F");
}

switch acts similar to the previous statement chain, by checking a value rather than a condition against a list of cases. If no matching case is found, then it moves on to execute the default case.

The following is the syntax for a switch statement:

switch (value)
{
    case case1:
        //code to execute
    [break;]
    case case2:
        //code to execute
    [break;]
    default:
        //code to execute
    [break;]
}

Provided below is an example of switch statement that outputs the corresponding season for the provided value of season.

int season = 3;
switch (season)
{
case 1:
    Console.WriteLine("Spring");
    break;
case 2:
    Console.WriteLine("Summer");
    break;
case 3:
    Console.WriteLine("Autumn");
    break;
case 4:
    Console.WriteLine("Winter");
    break;
}

Quiz

We've identified the following resources to provide additional context and learning for the content reviewed in this lesson. We encourage you to review the material below and explore additional related topics.

• C# Conditions