How to Join Strings in C#
The string.Join() method in C# concatenates elements of a collection with a specified separator. If you are looking for the practical answer to "string.join c#", the short version is that it is the cleanest way to join items from arrays, lists, or other collections.
string.Join() accepts any IEnumerable<T> and converts each element to a string automatically. For arrays and lists of strings, it is especially straightforward.
For complex scenarios with many concatenations, consider StringBuilder, but for simple joins, string.Join() is cleaner and just as efficient.
using System;
using System.Collections.Generic;
using System.Linq;
// Basic string.Join with array
string[] words = { "Hello", "World", "from", "C#" };
string sentence = string.Join(" ", words);
Console.WriteLine(sentence); // Hello World from C#
// Join with different separator
string csv = string.Join(", ", words);
Console.WriteLine(csv); // Hello, World, from, C#
// Join list of strings
List<string> names = new List<string> { "Alice", "Bob", "Charlie" };
string nameList = string.Join(", ", names);
Console.WriteLine($"Names: {nameList}");
// Join numbers (automatically converted to strings)
int[] numbers = { 1, 2, 3, 4, 5 };
string numberString = string.Join("-", numbers);
Console.WriteLine($"Numbers: {numberString}"); // 1-2-3-4-5
// Join with no separator
string noSep = string.Join("", new[] { "A", "B", "C" });
Console.WriteLine($"No separator: {noSep}"); // ABC
// Join with LINQ transformation
List<Person> people = new List<Person>
{
new Person("Alice", 25),
new Person("Bob", 30),
new Person("Charlie", 35)
};
string peopleNames = string.Join(", ", people.Select(p => p.Name));
Console.WriteLine($"People: {peopleNames}");
// Join with formatting
string formatted = string.Join(" | ", people.Select(p => $"{p.Name} ({p.Age})"));
Console.WriteLine($"Formatted: {formatted}");
// Join part of a collection
string[] colors = { "Red", "Green", "Blue", "Yellow", "Purple" };
string firstThree = string.Join(", ", colors.Take(3));
Console.WriteLine($"First three: {firstThree}");
// Multi-line join
string[] lines = { "Line 1", "Line 2", "Line 3" };
string multiLine = string.Join(Environment.NewLine, lines);
Console.WriteLine("Multi-line:");
Console.WriteLine(multiLine);
// Alternative: using + operator (less efficient in loops)
string manual = words[0] + " " + words[1] + " " + words[2];
Console.WriteLine($"\nManual concatenation: {manual}");
class Person
{
public string Name { get; set; }
public int Age { get; set; }
public Person(string name, int age)
{
Name = name;
Age = age;
}
}Take It Further
The community's favorite C# guide — teaches every concept you just read about with clarity.
The C# Player's Guide — 5th Edition · RB Whitaker
Get it on Amazon →As an Amazon Associate I earn from qualifying purchases.