C# String Interpolation is Easy

Mastering C# String Interpolation: A Comprehensive Guide

String interpolation is a useful feature in C# that allows you to format strings with variables, expressions, and methods. It improves code readability and maintainability. This post will cover basic concepts and more complex examples.

What is String Interpolation in C#?

String interpolation in C# is a syntactic sugar used to insert variables, expressions, or method results directly into a string using the syntax $"…" syntax, where variables or expressions are placed inside curly braces {}. This simplifies string formatting and improves code readability and maintainability.

Historical Context

Before the introduction of string interpolation in C#, .NET developers utilized various methods to format strings. One of the most commonly used methods was the String.Format method, which necessitated the use of placeholders in the form of curly braces with indices (such as {0}), which were then replaced with appropriate values. Despite being a powerful tool, String.Format often resulted in errors due to mismatched indices and values, making the code difficult to read and maintain.

C# 6.0, which was released in 2015 as part of the .NET Framework 4.6, introduced string interpolation. This feature simplifies the string formatting process and makes it more intuitive. Before this, even simple formatting tasks could require complex syntax and careful control over matching indexes and values in String.Format.

Basic Syntax of String Interpolation in C#

The syntax for string interpolation is as follows:

string interpolatedString = $"This is {variable}";

Here variable is a value that will be converted to a string and inserted in place of {variable}.

Examples and Explanations

Simple Example:

string name = "Aliaksandr";
string greeting = $"Hey there, {name}!";

This example illustrates how to use interpolation in C#.

Data Formatting.

String interpolation in C# enables formatting of inserted values:

double temperature = 19.39;
string message = $"The current temperature is {temperature:F1}°C";

The F1 in {temperature:F1} indicates that the temperature is formatted with one decimal place.

Advanced Usage

Conditional expressions can be used for interpolation.

String interpolation can be combined with the ternary operator to create conditional expressions:

int yourScore= 75;
string grade = $"Your grade is {(yourScore > 80 ? "A" : "B")}";

Interpolation and Loops.

String interpolation can also be used in loops to generate dynamic text:

for (int i = 1; i <= 10; i++) {
    Console.WriteLine($"Iteration number is {i}");

Multi-line Interpolation.

String interpolation allows for the use of multi-line literals:

string title = "Mr.";
string name = "Aliaksandr";
string address = "New York, USA";

string letter = $@"Dear {title} {name},
Welcome to {address}.
Your Team.";

Under the hood

String interpolation in C# is a mechanism that transforms a string literal with embedded expressions into a format that is treated like a normal string. The C# compiler translates an interpolated string into a series of calls that form the final string value.

At compile time, the interpolated string is converted to a string similar to one that could be generated using String.Format. For instance, the interpolated string $"Hi, {name}!" would be converted by the compiler to String.Format("Hi, {0}!", name). This conversion creates a formatted string and an array of objects to be inserted into that string.


String interpolation is a powerful tool for convenient and efficient string formatting. It makes code more readable and easily maintainable, reducing the risk of errors in the formatting process. This approach is especially valuable in scenarios where dynamic string generation is a frequent task, such as when generating UI messages or logs.

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