3. String manipulation

What is the primary implication of strings being 'immutable' in C#?

• The string will automatically be deleted from memory after its first use.
• The string can only contain numeric characters.
• The string cannot be changed once it has been created.
• The string must be declared using a value type rather than a reference type.

Answer explanation

Immutability means a string value remains unchanged after creation.

In C#, how do you include a double quote character inside a verbatim string literal?

• Use two consecutive double quotes ("").
• Use the Unicode sequence \u0022.
• Use a backslash followed by a quote (\").
• Use the @ symbol before the quote.

Answer explanation

Verbatim strings escape embedded quotes by doubling them.

Which escape sequence is used to trigger a carriage return in a standard string?

• \n
• \v
• \r
• \t

Answer explanation

\r is the standard escape sequence for a carriage return.

What is the result of the expression " hello ".Trim()?

• "hello"
• " hello"
• "hello "
• "h e l l o"

Answer explanation

Trim() removes leading and trailing whitespace from a string.

Given text = "Rain, rainbow, brain", what will text.Contains("RAIN", StringComparison.OrdinalIgnoreCase) return?

• true
• An IndexOutOfRangeException
• false
• null

Answer explanation

OrdinalIgnoreCase performs a case-insensitive search, so "RAIN" matches "Rain".

Which operator is used to perform a logical exclusive OR (XOR) on boolean operands?

• ^
• ||
• !
• &&

Answer explanation

The ^ operator represents boolean exclusive OR in C#.

According to the principles of lexical scope, what happens if you attempt to use a variable outside the curly braces in which it was declared?

• The variable becomes globally accessible to all classes.
• The program will run but use a value of zero for the variable.
• The compiler moves the declaration to the top of the file automatically.
• A compile-time error occurs because the variable is out of scope.

Answer explanation

A variable can only be used within the scope where it is declared.

What is the purpose of the break statement within a switch block?

• It forces the program to execute the default case.
• It pauses the program until the user presses a key.
• It exits the switch block immediately to prevent fall-through.
• It restarts the switch evaluation from the first case.

Answer explanation

break stops switch execution after the matching case runs.

If tempInCelsius is set to 15.0, which block will execute in an if(tempInCelsius < 20.0) statement?

• The 'if' block.
• Neither block.
• The 'else' block.
• Both the 'if' and 'else' blocks.

Answer explanation

Because 15.0 is less than 20.0, the if branch executes.

Why is it necessary to perform type conversion (such as converting to double) when reading input using Console.ReadLine()?

• Strings cannot be displayed in the console window.
• It prevents the user from entering special characters.
• Numbers are more memory-efficient than strings.
• Console.ReadLine() always returns data as a string.

Answer explanation

Console.ReadLine() returns text as a string, so numeric input must be converted before arithmetic.