string.Split() / string.Join()

string.Split(char separator)
string.Split(string separator)
string.Split(char[] separators)

string.Join(string separator, IEnumerable<string> values)
string.Join(string separator, string[] values)

Program.cs

using System;

// Use Split() to split a comma-separated string
string csvRow = "item_a,100,type_x,category_1,option_2";
string[] fields = csvRow.Split(',');
foreach (string field in fields) {
    Console.WriteLine(field);
}

This produces the following output:

dotnet run
item_a
100
type_x
category_1
option_2

Use string.Join() to concatenate array or list elements with a delimiter.

JoinSample.cs

using System;

// Join an array using string.Join()
string[] languages = { "C#", "Java", "Python" };
string joined = string.Join(" / ", languages);
Console.WriteLine(joined); // C# / Java / Python

// A common pattern: Split, process, then Join
string tagString = "csharp,dotnet,programming";
string[] tags = tagString.Split(',');
string result = string.Join(" | ", tags);
Console.WriteLine(result); // csharp | dotnet | programming

// Using a string as the delimiter
string sentence = "item_a, item_b, item_c";
string[] members = sentence.Split(", ");
Console.WriteLine(members[0]); // item_a
Console.WriteLine(members.Length); // 3

This produces the following output:

dotnet run
C# / Java / Python
csharp | dotnet | programming
item_a
3

Passing a char[] lets you split on any of multiple delimiter characters. Use StringSplitOptions.RemoveEmptyEntries to exclude empty elements.

MultiSeparator.cs

using System;

// Split on multiple delimiter characters
string text = "apple;banana,cherry|grape";
string[] items = text.Split(new char[] { ';', ',', '|' });
Console.WriteLine(string.Join(", ", items)); // apple, banana, cherry, grape

// When delimiters appear consecutively
string csv = "a,,b,,c";
string[] withEmpty = csv.Split(',');
Console.WriteLine(withEmpty.Length); // 5 (includes empty entries)

string[] noEmpty = csv.Split(',', StringSplitOptions.RemoveEmptyEntries);
Console.WriteLine(noEmpty.Length); // 3 (empty entries excluded)
Console.WriteLine(string.Join(", ", noEmpty)); // a, b, c

This produces the following output:

dotnet run
apple, banana, cherry, grape
5
3
a, b, c

Common Mistake: Empty Entries When Delimiters Are Consecutive

When delimiters appear consecutively or at the start/end of a string, Split() includes empty elements in the result array. Use StringSplitOptions.RemoveEmptyEntries to avoid unintended empty entries.

using System;

// NG: Consecutive delimiters produce empty entries
string csv = ",apple,,banana,";
string[] result = csv.Split(',');
Console.WriteLine(result.Length); // 5 (includes 3 empty entries)
foreach (string s in result) {
    Console.WriteLine($"[{s}]");
}

This produces the following output:

dotnet run
5
[]
[apple]
[]
[banana]
[]

Here is the source file used above:

using System;

// OK: Use RemoveEmptyEntries to exclude empty elements
string csv = ",apple,,banana,";
string[] result = csv.Split(',', StringSplitOptions.RemoveEmptyEntries);
Console.WriteLine(result.Length); // 2
foreach (string s in result) {
    Console.WriteLine($"[{s}]");
}

This produces the following output:

dotnet run
2
[apple]
[banana]

Split() is an instance method (called on a string instance), while string.Join() is a static method (called on the string class itself). Keep this distinction in mind.

If delimiters appear consecutively (e.g., "a,,b"), empty elements are included in the resulting array. To exclude empty entries, use Split(',', StringSplitOptions.RemoveEmptyEntries).

For string padding and formatting, see PadLeft() / PadRight().