Manipulate strings

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Text is one of the most common types of data in programming. In C#, text is represented as a string—a sequence of characters enclosed in double quotes. C# provides many built-in ways to manipulate and format strings.

Concatenation (joining strings together)

You can join two or more strings together into a single string using the + operator:

string first = "Hello";
string last = "world";
string message = first + ", " + last + "!";
Console.WriteLine(message);

Output:

Hello, world!

While concatenation works great for simple combinations, it can become messy when you try to mix variables, punctuation, and spaces together.

A better way: String interpolation

A cleaner, modern way to combine strings and variables is with string interpolation. To create this kind of string, place a dollar sign ($) directly before your opening quote, and place any variable names inside curly braces {}:

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

Output:

Hello, Alex!

You can try running this code yourself in the C# Code Editor.

A cleaner way to combine input and output

String interpolation solves the problem we saw earlier with Console.ReadLine(). Now you can mix text and variables easily:

string name = Console.ReadLine();
Console.WriteLine($"Hello, {name}! Nice to meet you.");

This is much cleaner than concatenating with +.

Note

If you forget the $ prefix (e.g., Console.WriteLine("Hello, {name}")), C# won't look inside the braces—it will literally print {name} on the screen.

Common string methods

C# strings have many built-in methods for common operations. To use a method, type the variable name, a dot, and the method name followed by parentheses:

Method	What it does	Example	Result
.ToUpper()	Converts text to uppercase	"hello".ToUpper()	"HELLO"
.ToLower()	Converts text to lowercase	"HELLO".ToLower()	"hello"
.Replace(old, new)	Swaps out specific characters	"cat".Replace("c", "b")	"bat"
.Length	Returns the number of characters	"Alex".Length	4

Practical example

Here's how you might use these techniques together:

Console.Write("What's your name? ");
string name = Console.ReadLine();
string greeting = $"Welcome, {name.ToUpper()}!";
Console.WriteLine(greeting);

If the user types alex, the output is:

What's your name? alex
Welcome, ALEX!

Notice how .ToUpper() converted the user's input to uppercase, and string interpolation made it easy to combine everything together.