Fun With Extension Methods - Extending String to Provide a Better Split Method

Do you feel that the standard Split implementation of the String class is a bit awkward to use? Do you keep forgetting you have to declare a char array for the separator? And do you often need to split on multiple characters, like \r\n to split on a line break? In that case, read on. A simple extension method might fix that for you.

Creating a Better Split Method

With the Split method on the String class, splitting a string in multiple lines separated by a \r would look like this:

char [] splitChar = { '\r' };
string source = "Text of First Line\rText of Second Line";
string[] result = source.Split(splitChar);

You define a char array that holds the line break character (\r) and then call Split. Not very intuitive. Also, with this implementation, it's impossible to split on multiple characters, like \r\n - the line break often used on Windows systems.

Normally, you would fix this by calling the Split method of the Regex class in the System.Text.RegularExpressions namespace. However, I often find that people don't know about this class or namespace or find them hard to discover.

With a simple extension method, you can combine the best of both worlds: extend the String class with a Split method that accepts one or more characters in a string. The method itself could easily delegate to the Regex class. To implement this, all you need is some code like this:

namespace MyExtensionMethods
  public static class StringExtensions
    /// <summary>
    /// Returns a string array that contains the substrings in this  
    /// string that are delimited by the specified string.		
    /// </summary>
    /// <param name="input">The input string to split.</param>
    /// <param name="separator">The string to split on like \r\n.</param>
    public static string[] Split(this string input, string separator)
      return System.Text.RegularExpressions.Regex.Split(input, separator);

With this code, all you need to do is add a using or Imports statement to your code for the MyExtensionMethods namespace, and then you can use Split like this:

string splitChars = "\r\n";
string source = "Text of First Line\r\nText of Second Line";
string[] result = source.Split(splitChars);

This gives you access to the Split method right where you'd expect it: directly on the String class.

Where to Next?

Wonder where to go next? You can read existing comments below or you can post a comment yourself on this article .

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On Monday, March 03, 2008 5:12:45 AM Muhammad said:

Can you tell me when I reference the Split Method to source object how will the Split method which you define in StringExtensions class will call?
On Monday, March 03, 2008 8:07:44 AM Imar Spaanjaars said:
Hi Muhammad,

I don't understand what you are asking. If you are new to extension methods and want to know how they work, check out this post:


On Wednesday, May 14, 2008 10:20:12 PM Vladimir Kelman said:
A good one too.

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