How to split strings efficiently in C#

String manipulation, such as splitting, is common in many applications, but it can be resource-intensive if not handled efficiently. In particular, using the String.Split() method in C# can cause unnecessary memory allocations, making it unsuitable for performance-critical scenarios. A better alternative is the ReadOnlySpan<char>.Split() method, which allows for more efficient string splitting with minimal resource overhead.

Why Split Strings?

String splitting is often required in various tasks like:

• Processing large text files
• Parsing command-line arguments
• Tokenizing a string
• Parsing CSV files or log files

When dealing with large datasets, breaking a string into smaller parts using delimiters is a common task. While the String.Split() method is typically used for this, its performance may be an issue in scenarios where efficiency is crucial.

Using String.Split() Method

The String.Split() method can also be used to split a string containing email addresses, separated by semicolons, into individual email addresses.

string emails = "[email protected]; [email protected]; [email protected]";
char[] delimiters = new char[] { ';' };
string[] emailList = emails.Split(delimiters, 
    StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);

foreach (string email in emailList)
{
    Console.WriteLine(email);
}

The method creates a new array of strings for each segment, which leads to higher memory consumption, especially when working with large strings.

Using ReadOnlySpan<char>.Split() Method

The ReadOnlySpan<char> struct introduced in .NET 9 provides a more efficient way to handle string splitting. Instead of allocating new strings for each segment, it returns slices of the original string, avoiding memory allocations and reducing overhead.

ReadOnlySpan<char> productNames = "Laptop, Smartphone, Tablet, Smartwatch, Headphones";
char[] delimiters = new[] { ',' };

foreach (Range segment in productNames.Split(delimiters))
{
    Console.WriteLine(productNames[segment].ToString().Trim());
}

With ReadOnlySpan<char>, no new memory allocations are made when splitting the string. Instead, the substrings reference the original span, meaning the data is accessed more efficiently.

For applications where performance and memory management are critical, using ReadOnlySpan<char>.Split() is a more efficient alternative to the String.Split() method. It reduces memory allocations and overhead by referencing substrings instead of creating new ones, making it ideal for scenarios involving large strings or frequent string operations.