When working with C#, one of the most commonly used data types is the C# string. Strings are everywhere—whether you're displaying a user’s name, storing an email address, or formatting output for a report. Understanding how to work with strings effectively is an essential skill for any C# developer.
In this post, we’ll explore what strings are, how they work in memory, and how to use important string methods, formatting techniques, and manipulation operations in C#.
What is a String in C#?
In C#, a string is a sequence of characters. It’s represented by the System.String class and can hold text data like words, sentences, or even numbers as text.
You can create a string simply by enclosing characters inside double quotes:
string message = "Hello, World!";
Behind the scenes, the string type in C# is an object, not a primitive data type. This means it comes with built-in methods and properties you can use to manipulate and analyze text.
Strings Are Immutable
Before diving into manipulation, it’s important to understand that strings in C# are immutable.
This means once a string is created, its value cannot be changed in memory. If you modify a string, C# actually creates a new string in memory instead of altering the original one.
For example:
string name = "Suraj";
name += " Kumar";
Console.WriteLine(name);
Here, "Suraj" and "Kumar" form a new string "Suraj Kumar". The original "Suraj" string remains unchanged.
This immutability makes string operations safe but can affect performance in cases where a lot of modifications are required — in such cases, using the StringBuilder class is more efficient.
Common String Methods in C#
C# provides a rich set of methods to work with strings. Let’s look at some of the most commonly used ones:
- Length
Returns the number of characters in a string.
string city = "Noida";
Console.WriteLine(city.Length); // Output: 5
- ToUpper() and ToLower()
Used to convert text to uppercase or lowercase.
string text = "Hello";
Console.WriteLine(text.ToUpper()); // HELLO
Console.WriteLine(text.ToLower()); // hello
- Substring()
Extracts a portion of a string based on the starting index.
string word = "Programming";
string part = word.Substring(0, 7);
Console.WriteLine(part); // Program
- Contains()
Checks if a string contains another substring.
string sentence = "C# is fun!";
Console.WriteLine(sentence.Contains("fun")); // True
- Replace()
Replaces all occurrences of a character or substring with another.
string data = "C# is easy";
string result = data.Replace("easy", "powerful");
Console.WriteLine(result); // C# is powerful
- Trim()
Removes whitespace from the start and end of a string.
string name = " Suraj Kumar ";
Console.WriteLine(name.Trim()); // "Suraj Kumar"
- Split() and Join()
Used for breaking a string into parts and joining them back.
string names = "Amit, Raj, Neha";
string[] list = names.Split(',');
foreach (string n in list)
{
Console.WriteLine(n.Trim());
}
And you can join them back:
string combined = string.Join(" | ", list);
Console.WriteLine(combined); // Amit | Raj | Neha
String Formatting in C#
Formatting strings helps make your output more readable and structured. C# supports several ways to format strings:
1. Using String Concatenation
string first = "Suraj";
string last = "Kumar";
string fullName = first + " " + last;
Console.WriteLine(fullName);
2. Using String.Format()
string name = "Ravi";
int age = 25;
string info = string.Format("Name: {0}, Age: {1}", name, age);
Console.WriteLine(info);
3. String Interpolation (Recommended)
Introduced in C# 6.0, string interpolation provides a cleaner syntax.
string user = "Anjali";
int score = 89;
Console.WriteLine($"Student {user} scored {score} marks.");
4. Composite Formatting
You can also format numbers, dates, or currencies.
double price = 1999.99;
Console.WriteLine($"Price: {price:C}");
Output:
Price: ₹1,999.99
Manipulating Strings
You can perform various manipulations such as reversing, searching, or comparing strings.
1. Reversing a String
string word = "CSharp";
char[] arr = word.ToCharArray();
Array.Reverse(arr);
string reversed = new string(arr);
Console.WriteLine(reversed); // prahSC
2. Comparing Strings
C# offers different methods for comparison.
string a = "hello";
string b = "Hello";
Console.WriteLine(a.Equals(b)); // False
Console.WriteLine(a.Equals(b, StringComparison.OrdinalIgnoreCase)); // True
3. Checking Start or End
string file = "data.txt";
Console.WriteLine(file.StartsWith("data")); // True
Console.WriteLine(file.EndsWith(".txt")); // True
Using StringBuilder for Better Performance
When you perform many concatenations, use StringBuilder from the System.Text namespace. It avoids creating multiple string objects in memory.
using System.Text;
StringBuilder sb = new StringBuilder();
sb.Append("Learning ");
sb.Append("C# ");
sb.Append("Strings");
Console.WriteLine(sb.ToString());
StringBuilder is mutable, which means it modifies data in the same memory location — ideal for loops or dynamic text generation.
Conclusion
Strings are one of the most powerful and frequently used data types in C#. Understanding how they work and how to use built-in methods can make your code cleaner, faster, and easier to maintain. Whether you’re formatting output, comparing data, or manipulating text, C# provides every tool you need through its String class and StringBuilder.
By mastering these string operations, you’ll find everyday programming tasks simpler and more efficient — and you’ll write C# code that’s both elegant and powerful.
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