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

Recall & Review

beginner

What is string interpolation in C#?

String interpolation is a way to insert variables or expressions directly inside a string literal using a special syntax, making the code easier to read and write.

beginner

How do you start a string literal to use string interpolation in C#?

You start the string with a $ symbol before the opening double quote, like this: $"Your text {variable}".

beginner

What is the output of this code?<br>

int age = 25;<br>string message = $"I am {age} years old.";<br>Console.WriteLine(message);

The output will be: I am 25 years old.

intermediate

Can you use expressions inside the curly braces in string interpolation?

Yes, you can put any valid expression inside the curly braces, like calculations or method calls, and it will be evaluated and inserted into the string.

intermediate

How do you format numbers or dates inside string interpolation?

You can add a colon and a format string after the expression inside the braces, for example: $"{price:C}" to format as currency or $"{date:yyyy-MM-dd}" for a date format.

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

A $

B #

C @

D %

In C#, string interpolation requires a $ symbol before the opening quote.

What will this code print?<br>

int x = 3;<br>int y = 4;<br>Console.WriteLine($"Sum is {x + y}");

A Sum is x + y

B Sum is {x + y}

C Sum is 34

D Sum is 7

The expression inside braces is evaluated, so 3 + 4 = 7.

How do you include a literal curly brace '{' in an interpolated string?

A Use single quotes '{'

B Escape with backslash '\{'

C Use double braces like '{{'

D You cannot include curly braces

Double braces '{{' or '}}' are used to include literal curly braces in interpolated strings.

Which of these is a valid interpolated string in C#?

A $"Hello {name}"

B "Hello {name}"

C @"Hello {name}"

D #"Hello {name}"

Only the string starting with $ supports interpolation.

How can you format a date inside an interpolated string?

A "{date}"

B $"{date:MM/dd/yyyy}"

C "{date:MM/dd/yyyy}"

D $"{date.format('MM/dd/yyyy')}"

You use a colon and format string inside the braces to format dates.

Explain how string interpolation works in C# and give a simple example.

Think about how to insert a variable value directly inside a string.

Describe how to format numbers or dates inside an interpolated string in C#.

Remember the syntax {expression:format} inside the string.