String.Split Method (String[], StringSplitOptions)

Updated: September 2010

Returns a string array that contains the substrings in this string that are delimited by elements of a specified string array. A parameter specifies whether to return empty array elements.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

[ComVisibleAttribute(false)]
public string[] Split(
	string[] separator,
	StringSplitOptions options
)

Parameters

separator
Type: System.String[]

An array of strings that delimit the substrings in this string, an empty array that contains no delimiters, or null.

options
Type: System.StringSplitOptions

Specify RemoveEmptyEntries to omit empty array elements from the array returned, or None to include empty array elements in the array returned.

Return Value

Type: System.String[]
An array whose elements contain the substrings in this string that are delimited by one or more strings in separator. For more information, see the Remarks section.

ExceptionCondition
ArgumentException

options is not one of the StringSplitOptions values.

Return Value Details

Delimiter strings are not included in the elements of the returned array.

If this instance does not contain any of the strings in separator, the returned array consists of a single element that contains this instance. If the separator parameter is null or contains no characters, white-space characters are assumed to be the delimiters. For a list of the characters that the Split method interprets as white space, see the table in the Remarks section of the String.Split(Char[]) method. (Note that this list is slightly different from the list of white-space characters recognized by the Trim() method.)

If the separator parameter in the call to this method overload is null, compiler overload resolution fails. To unambiguously identify the called method, your code must indicate the type of the null. The following example shows several ways to unambiguously identify this overload.

string phrase = "The quick  brown fox";
string[] words;

words = phrase.Split(default(string[]), StringSplitOptions.RemoveEmptyEntries);

words = phrase.Split((string[]) null, StringSplitOptions.RemoveEmptyEntries);

words = phrase.Split(null as string[], StringSplitOptions.RemoveEmptyEntries);

If the options parameter is RemoveEmptyEntries and the length of this instance is zero, an empty array is returned.

Each element of separator defines a separate delimiter character. If the options parameter is None, and two delimiters are adjacent or a delimiter is found at the beginning or end of this instance, the corresponding array element contains Empty.

Comparison Details

The Split method extracts the substrings in this string that are delimited by one or more of the strings in the separator parameter, and returns those substrings as elements of an array.

The Split method looks for delimiters by performing comparisons using case-sensitive ordinal sort rules. For more information about word, string, and ordinal sorts, see the System.Globalization.CompareOptions enumeration.

The Split method ignores any element of separator whose value is null or the empty string ("").

To avoid ambiguous results when strings in separator have characters in common, the Split operation proceeds from the beginning to the end of the value of the instance, and matches the first element in separator that is equal to a delimiter in the instance. The order in which substrings are encountered in the instance takes precedence over the order of elements in separator.

For example, consider an instance whose value is "abcdef". If the first element in separator was "ef" and the second element was "bcde", the result of the split operation would be "a" and "f". This is because the substring in the instance, "bcde", is encountered and matches an element in separator before the substring "f" is encountered.

However, if the first element of separator was "bcd" and the second element was "bc", the result of the split operation would be "a" and "ef". This is because "bcd" is the first delimiter in separator that matches a delimiter in the instance. If the order of the separators was reversed so the first element was "bc" and the second element was "bcd", the result would be "a" and "def".

Performance Considerations

The Split methods allocate memory for the returned array object and a String object for each array element. If your application requires optimal performance or if managing memory allocation is critical in your application, consider using the IndexOf or IndexOfAny method, and optionally the Compare method, to locate a substring within a string.

If you are splitting a string at a separator character, use the IndexOf or IndexOfAny method to locate a separator character in the string. If you are splitting a string at a separator string, use the IndexOf or IndexOfAny method to locate the first character of the separator string. Then use the Compare method to determine whether the characters after that first character are equal to the remaining characters of the separator string.

In addition, if the same set of characters is used to split strings in multiple Split method calls, consider creating a single array and referencing it in each method call. This significantly reduces the additional overhead of each method call.

The following example illustrates the difference in the arrays returned by calling a string's String.Split(String[], StringSplitOptions) method with its options parameter equal to StringSplitOptions.None and StringSplitOptions.RemoveEmptyEntries.

string source = "[stop]ONE[stop][stop]TWO[stop][stop][stop]THREE[stop][stop]";
string[] stringSeparators = new string[] {"[stop]"};
string[] result;

// Display the original string and delimiter string.
Console.WriteLine("Splitting the string:\n   \"{0}\".", source);
Console.WriteLine();
Console.WriteLine("Using the delimiter string:\n   \"{0}\"", 
                  stringSeparators[0]);
Console.WriteLine();                           

// Split a string delimited by another string and return all elements.
result = source.Split(stringSeparators, StringSplitOptions.None);
Console.WriteLine("Result including all elements ({0} elements):", 
                  result.Length);
Console.Write("   ");
foreach (string s in result)
{
   Console.Write("'{0}' ", String.IsNullOrEmpty(s) ? "<>" : s);                   
}
Console.WriteLine();
Console.WriteLine();

// Split delimited by another string and return all non-empty elements.
result = source.Split(stringSeparators, 
                      StringSplitOptions.RemoveEmptyEntries);
Console.WriteLine("Result including non-empty elements ({0} elements):", 
                  result.Length);
Console.Write("   ");
foreach (string s in result)
{
   Console.Write("'{0}' ", String.IsNullOrEmpty(s) ? "<>" : s);                   
}
Console.WriteLine();
/*
This example displays the following output to the console:

Splitting the string:
   "[stop]ONE[stop][stop]TWO[stop][stop][stop]THREE[stop][stop]".
Using the delimiter string:
   "[stop]"

Result using StringSplitOptions.None (all elements):
   '<>' 'ONE' '<>' 'TWO' '<>' '<>' 'THREE' '<>' '<>'

Result using StringSplitOptions.RemoveEmptyEntries:
   'ONE' 'TWO' 'THREE'
*/      

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0

Date

History

Reason

September 2010

Addressed compiler overload resolution in the Remarks section.

Customer feedback.

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