String interpolation and formatting in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is string interpolation in C#?

String interpolation in C# is a way to insert variables or expressions directly inside a string literal by prefixing the string with a $ symbol and placing the expressions inside curly braces {}.

beginner

How do you format a number to show two decimal places using string interpolation?

Use a format specifier inside the curly braces, like this: $"{number:F2}". This will format the number to two decimal places.

intermediate

What is the difference between String.Format and string interpolation?

String.Format is a method that formats strings using placeholders like {0}, {1}, etc., while string interpolation lets you embed expressions directly in the string with $ and {}. Interpolation is usually easier to read and write.

intermediate

How can you align text using string interpolation?

Inside the curly braces, after the variable name, use a comma and a number to specify alignment. For example, $"{name,10}" right-aligns in 10 spaces, and $"{name,-10}" left-aligns.

advanced

What happens if you use a format specifier that doesn't match the data type in string interpolation?

You will get a runtime error or unexpected output because the format specifier expects a certain type. For example, using a numeric format on a string will cause an error.

Which symbol is used to start a string interpolation in C#?

A $

B #

C @

D %

String interpolation in C# starts with the $ symbol before the string.

How do you format a number to show exactly 3 decimal places using string interpolation?

A {number:3}

B {number:F3}

C {number:.3f}

D {number:#.###}

The format specifier F3 formats the number to 3 decimal places in C#.

What does this code output? string name = "Bob"; Console.WriteLine($"{name,5}");

A Bob (right-aligned in 5 spaces)

B Bob (left-aligned in 5 spaces)

C Bob (no spaces)

D Error

The comma 5 right-aligns the text in a field of width 5, so spaces appear before 'Bob'.

Which method is an alternative to string interpolation for formatting strings?

A ToString()

B Console.Write

C String.Format

D Parse()

String.Format uses placeholders and is an older way to format strings.

What will happen if you use {value:D2} where value is a string?

A Outputs 'D2'

B Formats string as decimal with 2 digits

C Outputs the string unchanged

D Throws a runtime error

The 'D2' format specifier expects a number; using it on a string causes a runtime error.

Explain how to use string interpolation in C# to include variables and format numbers.

Think about how you write variables inside a string with $ and {}.

Describe how to align text using string interpolation in C#.

Remember the syntax {variable,number} inside the string.