C# 0 The Complete Reference

StringSplitOptions

enumeration defines only two values: 

None

 and

 RemoveEmptyEntries

. If 

how

 is 

None

,

then empty strings are included in the result (as the previous program showed). If 

how

 is 

RemoveEmptyEntries

, empty strings are excluded from the result.

To understand the effects of removing empty entries, try replacing this line in the 

preceding program:

string[] parts = str.Split(seps);

with the following:

string[] parts = str.Split(seps, StringSplitOptions.RemoveEmptyEntries);

When you run the program, the output will be as shown next:

Pieces from split:

One

if

by

land

two

if

by

sea

Result of join:

One | if | by | land | two | if | by | sea

As you can see, the empty string that previously resulted because of the combination of the 

comma and space after “land” has been removed.

Splitting a string is an important string-manipulation procedure because it is often used 

to obtain the individual 

tokens

 that comprise the string. For example, a database program 

might use 

Split( )

 to decompose a query such as “show me all balances greater than 100” 

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into its individual parts, such as “show” and “100”. In the process, the separators are 

removed. Thus, “show” (without any leading or trailing spaces) is obtained, not “ show”. The 

following program illustrates this concept. It tokenizes strings containing binary mathematical 

operations, such as 10 + 5. It then performs the operation and displays the result.

// Tokenize strings.

using System;

class TokenizeDemo {

  static void Main() {

    string[] input = {

                      "100 + 19",

                      "100 / 3.3",

                      "-3 * 9",

                      "100 - 87"

                     };

    char[] seps = {' '};

    for(int i=0; i < input.Length; i++) {

      // split string into parts

      string[] parts = input[i].Split(seps);

      Console.Write("Command: ");

      for(int j=0; j < parts.Length; j++)

        Console.Write(parts[j] + " ");

      Console.Write(", Result: ");

      double n = Double.Parse(parts[0]);

      double n2 = Double.Parse(parts[2]);

      switch(parts[1]) {

        case "+":

          Console.WriteLine(n + n2);

          break;

        case "-":

          Console.WriteLine(n - n2);

          break;

        case "*":

          Console.WriteLine(n * n2);

          break;

        case "/":

          Console.WriteLine(n / n2);

          break;

      }

    }

  }

}

Here is the output:

Command: 100 + 19 , Result: 119

Command: 100 / 3.3 , Result: 30.3030303030303

Command: -3 * 9 , Result: -27

Command: 100 - 87 , Result: 13

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