Compile and run

Learn to compile and run a C# program with dotnet run and dotnet build.

String interpolation

String interpolation is a way to embed a variable or expression inside text. You start the string with the $ sign and put the expression you want to embed inside curly braces { }.

string name = "Alex";
Console.WriteLine($"Hello, {name}!");

The {name} expression is replaced by the variable's value. Output: Hello, Alex! This is more readable than concatenating strings.

The string variable

To store text for later use you declare a string variable. A variable holds a value and lets you reuse it any time.

string name = "Alex";

Here name is the variable's name and "Alex" is the value it holds. Variable names use English letters and start with lowercase. You can change the value later.

Exercise Print a message with interpolation

Declare a string name variable (example: "Alex") and print Hello, Alex! using string interpolation with Console.WriteLine.

Show example solution

First write string name = "Alex";, then Console.WriteLine($"Hello, {name}!");.
Example solution:
using System;

class Program
{
    static void Main()
    {
        // Define a string variable
        string name = "Alex";
        // Print the message with interpolation
        Console.WriteLine($"Hello, {name}!");
    }
}

Test yourself

Which is a valid interpolated string?
- Console.WriteLine("Hello");
- Console.WriteLine($"Hello, {name}!");
- Console.WriteLine("Hello, {name}!");
- Console.WriteLine(Hello, {name}!);
Show answer

Console.WriteLine($"Hello, {name}!"); — Correct! The $ prefix marks interpolation and {name} is embedded.

Interpolation prefix

Console.WriteLine(____"Hello, {name}!");

Show answer

Console.WriteLine($"Hello, {name}!");

Match the interpolation concepts

$

Interpolation prefix
{ }

Embedding expression
string

Variable type
WriteLine

Output method

Next lesson: Summary - C# basics

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