C# String Interpolation
Last modified April 18, 2025
This tutorial explores how to perform string interpolation in C#.
In C#, strings can be constructed using either string formatting or string interpolation. This tutorial focuses on the latter approach.
String interpolation involves embedding expressions within a string
literal, replacing them with their evaluated results. A string prefixed with the
$ character is an interpolated string, and expressions are enclosed
in curly braces {}.
An interpolated expression has the following structure:
{<interpolationExpression>[,<alignment>][:<formatString>]}
The interpolationExpression is the expression evaluated to produce
the result. The alignment specifies the minimum width of the
result's string representation. The formatString defines the
formatting style of the result.
Simple Example
This example demonstrates basic string interpolation in C#.
string name = "John Doe";
int age = 34;
Console.WriteLine($"{name} is {age} years old");
DateTime now = DateTime.Now;
Console.WriteLine($"Today is {now.DayOfWeek}, it's {now:HH:mm}");
The program creates two interpolated strings with variables and a formatted date.
string name = "John Doe"; int age = 34;
Two variables are defined for use in the first interpolated string.
Console.WriteLine($"{name} is {age} years old");
The $ prefix marks the interpolated string, and variables
are inserted within curly braces {}.
$ dotnet run John Doe is 34 years old Today is Sunday, it's 22:12
String Interpolation Alignment
This example shows how to align text in interpolated strings.
List<User> users =
[
new ("John", "Doe", 1230),
new ("Lucy", "Novak", 670),
new ("Ben", "Walter", 2050),
new ("Robin", "Brown", 2300),
new ("Amy", "Doe", 1250),
new ("Joe", "Draker", 1190),
new ("Janet", "Doe", 980),
new ("Albert", "Novak", 1930),
];
foreach (var user in users)
{
string fname = $"{user.FirstName} {user.LastName}";
Console.WriteLine($"|{fname, -15}|{user.Salary, 8}|");
}
record User(string FirstName, string LastName, int Salary);
The program displays a list of users, aligning names to the left and salaries to the right.
string fname = $"{user.FirstName} {user.LastName}";
The first and last names are combined into a full name using interpolation.
Console.WriteLine($"|{fname, -15}|{user.Salary, 8}|");
A negative alignment value left-aligns the text, while a positive value right-aligns it.
$ dotnet run |John Doe | 1230| |Lucy Novak | 670| |Ben Walter | 2050| |Robin Brown | 2300| |Amy Doe | 1250| |Joe Draker | 1190| |Janet Doe | 980| |Albert Novak | 1930|
Format Strings
This example applies format strings to interpolated expressions.
DateTime now = DateTime.Now;
Console.WriteLine($"Short date: {now:d}");
Console.WriteLine($"Long date: {now:D}");
Console.WriteLine($"Short time: {now:t}");
Console.WriteLine($"Long time: {now:T}");
Console.WriteLine($"Month: {now:M}");
Console.WriteLine($"Year: {now:Y}");
The program formats the current date and time using various format specifiers in interpolated strings.
$ dotnet run Short date: 19. 1. 2024 Long date: Friday, January 19, 2024 Short time: 11:19 Long time: 11:19:22 Month: January 19 Year: January 2024
Interpolated Strings with Newlines
Since C# 11, interpolated strings can include newlines for improved readability.
List<User> users =
[
new ("John", "Doe", 1230),
new ("Lucy", "Novak", 670),
new ("Ben", "Walter", 2050),
new ("Robin", "Brown", 2300),
new ("Amy", "Doe", 1250),
new ("Joe", "Draker", 1190),
new ("Janet", "Doe", 980),
new ("Albert", "Novak", 1930),
];
Console.WriteLine($"User with highest salary:\n{
users.MaxBy(u => u.Salary)
}");
record User(string FirstName, string LastName, int Salary);
The program embeds a multiline LINQ expression within an interpolated string, enhancing code clarity.
$ dotnet run
User with highest salary:
User { FirstName = Robin, LastName = Brown, Salary = 2300 }
Raw Strings
Introduced in C# 11, raw strings allow unescaped text and are enclosed by at least three double quotes.
var countries = new Dictionary<string, string>
{
{"Russia", "Moscow"},
{"Slovakia", "Bratislava"},
{"Germany", "Berlin"},
{"Hungary", "Budapest"},
};
foreach (var (k, v) in countries)
{
Console.WriteLine($"""The capital of "{k}" is "{v}" """);
}
Raw strings simplify handling text with quotes, as no escape sequences are needed.
$ dotnet run The capital of "Russia" is "Moscow" The capital of "Slovakia" is "Bratislava" The capital of "Germany" is "Berlin" The capital of "Hungary" is "Budapest"
Conditional Operator
When using a conditional operator in interpolation, enclose the colon in parentheses to avoid conflicts.
var items = new Dictionary<string, int>
{
{"ring", 2},
{"lamp", 1},
{"chair", 3},
{"coin", 5},
{"TV", 4},
{"book", 4},
{"pen", 1},
};
Console.WriteLine("List of items:");
foreach (var (k, v) in items)
{
Console.WriteLine($"""{v} {k}{(v == 1 ? "" : "s")}""");
}
The program uses a conditional operator within an interpolated string to handle pluralization.
$ dotnet run List of items: 2 rings 1 lamp 3 chairs 5 coins 4 TVs 4 books 1 pen
Number Formatting
This example demonstrates formatting numbers in interpolated strings.
double price = 49.99;
int quantity = 3;
Console.WriteLine($"Total cost: {price * quantity:C}");
Console.WriteLine($"Price per item: {price:F2}");
Console.WriteLine($"Quantity: {quantity:D3}");
The program formats currency, fixed-point, and padded integer values using format specifiers.
$ dotnet run Total cost: $149.97 Price per item: 49.99 Quantity: 003
String Interpolation with Expressions
Interpolated strings can include complex expressions for dynamic content.
int x = 5;
int y = 10;
Console.WriteLine($"The sum of {x} and {y} is {x + y}");
Console.WriteLine($"The product is {x * y}");
Console.WriteLine($"Is {x} less than {y}? {(x < y ? "Yes" : "No")}");
The program embeds arithmetic and conditional expressions within interpolated strings.
$ dotnet run The sum of 5 and 10 is 15 The product is 50 Is 5 less than 10? Yes
Interpolated Strings with Collections
This example uses interpolation to format collection data concisely.
List<string> fruits = ["apple", "banana", "orange"];
Console.WriteLine($"Favorite fruits: {string.Join(", ", fruits)}");
Console.WriteLine($"Total fruits: {fruits.Count}");
The program combines collection data and string joining within an interpolated string.
$ dotnet run Favorite fruits: apple, banana, orange Total fruits: 3
Multiline Raw Interpolated Strings
Raw interpolated strings can span multiple lines for complex formatting.
string name = "Alice";
int score = 95;
string message = $"""
Dear {name},
Your score is {score}.
{(score >= 90 ? "Excellent work!" : "Keep practicing!")}
""";
Console.WriteLine(message);
The program uses a multiline raw interpolated string with embedded expressions for a formatted message.
$ dotnet run Dear Alice, Your score is 95. Excellent work!
Source
This tutorial has demonstrated various techniques for string interpolation in C#.
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