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String.Split Method (String[], Int32, StringSplitOptions)

Returns a string array that contains the substrings in this string that are delimited by elements of a specified string array. Parameters specify the maximum number of substrings to return and whether to return empty array elements.

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

[<ComVisibleAttribute(false)>]
member Split : 
        separator:string[] * 
        count:int * 
        options:StringSplitOptions -> string[] 

Parameters

separator
Type: System.String[]
An array of strings that delimit the substrings in this string, an empty array that contains no delimiters, or a null reference (Nothing in Visual Basic).
count
Type: System.Int32
The maximum number of substrings to return.
options
Type: System.StringSplitOptions
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
ArgumentOutOfRangeException

count is negative.

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, or the count parameter is 1, the returned array consists of a single element that contains this instance. If the separator parameter is a null reference (Nothing in Visual Basic) or contains no characters, white-space characters are assumed to be the delimiters. White-space characters are defined by the Unicode standard and return true if they are passed to the Char.IsWhiteSpace method. However, if the separator parameter in the call to this method overload is a null reference (Nothing in Visual Basic), compiler overload resolution fails. To unambiguously identify the called method, your code must indicate the type of the a null reference (Nothing in Visual Basic). The following example shows several ways to unambiguously identify this overload.

No code example is currently available or this language may not be supported.

If the count parameter is zero, or 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 that consists of one or more characters. 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.

If there are more than count substrings in this instance, the first count minus 1 substrings are returned in the first count minus 1 elements of the return value, and the remaining characters in this instance are returned in the last element of the return value.

If count is greater than the number of substrings, the available substrings are returned and no exception is thrown.

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 a null reference (Nothing in Visual Basic) or the empty string ("").

To avoid ambiguous results when strings in separator have characters in common, the Split method 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.

Notes to Callers

In the .NET Framework 3.5 and earlier versions, if the Split method is passed a separator that is a null reference (Nothing in Visual Basic) or contains no characters, the method uses a slightly different set of characters to split the string than the Trim method does to trim the string. In the .NET Framework 4, both methods use an identical set of Unicode white-space characters.

The following example uses the StringSplitOptions enumeration to include or exclude substrings generated by the Split method.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

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