VB.NET Split String Examples

Separate strings on a value with the String.Split function. Use Char and String delimiters.
Split. This function separates Strings. It receives a string or character delimiter. It parses and separates the source string by getting the parts that come between the delimiter.
Split, notes. We receive a String array of varying size from Split. With RemoveEmptyEntries (an enum) we can eliminate empty strings from the result of Split.ArrayEnum
First example. Here we break apart a string on the spaces in the string. We pass a Char array to Split with a single space in it. We loop over the resulting words and display them.

Char array: The "New Char" syntax is used to create the char array. This is a one-element char array, with one space char.

Char Array
VB.NET program that uses Split Module Module1 Sub Main() ' We want to split this input string. Dim s As String = "there is a cat" ' Split string based on spaces. Dim words As String() = s.Split(New Char() {" "c}) ' Use For Each loop over words and display them. For Each word As String In words Console.WriteLine("WORD: {0}", word) Next End Sub End Module Output WORD: there WORD: is WORD: a WORD: cat
File path parts. Here we split a file system path into separate parts. We use a New Char array with one string containing a backslash. We then loop through and display the results.
VB.NET program that splits file path Module Module1 Sub Main() ' The file system path we need to split. Dim s As String = "C:\Users\Sam\Documents\Perls\Main" ' Split the string on the backslash character. Dim parts As String() = s.Split(New Char() {"\"c}) ' Loop through result strings with For Each. Dim part As String For Each part In parts Console.WriteLine(part) Next End Sub End Module Output C: Users Sam Documents Perls Main
Regex.Split words. Often we need to extract words from a String. The code here needs to handle punctuation and non-word characters differently than the String Split function.Regex.Split

Argument 1: The first argument to Regex.Split is the source string we are trying to separate apart.

Argument 2: The second argument is a Regex pattern. The pattern "\W+" is used, and this means "one or more non-word characters".

Warning: Regex functions tend to be slower. But they can handle more complex patterns than the String Split function.

VB.NET program that splits words Imports System.Text.RegularExpressions Module Module1 Sub Main() ' Declare iteration variable. Dim s As String ' Loop through words in string. Dim arr As String() = SplitWords("That is a cute cat, man!") ' Display each word. ' ... Note that punctuation is handled correctly. For Each s In arr Console.WriteLine(s) Next Console.ReadLine() End Sub ''' <summary> ''' Split the words in string on non-word characters. ''' This means commas and periods are handled correctly. ''' </summary> Private Function SplitWords(ByVal s As String) As String() ' Call Regex.Split function from the imported namespace. ' ... Return the result array. Return Regex.Split(s, "\W+") End Function End Module Output That is a cute cat man
File lines. Here we Split each line in a file using the File.ReadAllLines Function and Split. We have a comma-separated-values (CSV) file. We first read in the file with ReadAllLines.

Info: The File.ReadAllLines Function puts each line in the file into an array, which we can loop over.


Split: We call Split() with a Char array with 1 element—the comma char. This separates each line on the comma.

Input file used frontal,parietal,occipital,temporal pulmonary artery,aorta,left ventricle VB.NET program that splits lines Imports System.IO Module Module1 Sub Main() Dim i As Integer = 0 ' Loop through each line in array returned by ReadAllLines. Dim line As String For Each line In File.ReadAllLines("example.txt") ' Split line on comma. Dim parts As String() = line.Split(New Char() {","c}) ' Loop over each string received. Dim part As String For Each part In parts ' Display to console. Console.WriteLine("{0}:{1}", i, part) Next i += 1 Next End Sub End Module Output 0:frontal 0:parietal 0:occipital 0:temporal 1:pulmonary artery 1:aorta 1:left ventricle
RemoveEmptyEntries. Sometimes there are no characters between two delimiters. This results in an empty string in the result array.

Argument 1: We pass a character array as the first argument. We specify we want to split on a comma char.

Argument 2: We pass RemoveEmptyEntries as the second argument. This avoids empty strings in the result array.

Result: Two empty elements are removed. If we use Split() without RemoveEmptyEntries, 2 additional strings are returned.

VB.NET program that uses RemoveEmptyEntries Module Module1 Sub Main() Dim value As String = "cat,dog,,,fish" ' Split string on comma characters. ' ... Remove empty elements from result. Dim elements() As String = value.Split(New Char() {","c}, StringSplitOptions.RemoveEmptyEntries) ' Display elements. For Each element As String In elements Console.WriteLine(element) Next End Sub End Module Output cat dog fish
Performance, char split. Suppose we need to split on a 1-character string. We could use a 1-char String in a String array, or a Char in a Char array. The performance may be affected.Benchmarks

Version 1: We split on a 1-char String. The result here has 3 Strings—the string is split on a comma.

Version 2: We call Split directly on a Char. This version is slightly faster—we should use a Char array when possible.

VB.NET program that tests char array split performance Module Module1 Sub Main() Dim m As Integer = 10000000 ' Version 1: split on string array. Dim s1 As Stopwatch = Stopwatch.StartNew For i As Integer = 0 To m - 1 Dim result() As String = "cat,frog,dog".Split(New String() {","}, StringSplitOptions.None) If result.Length <> 3 Then Return End If Next s1.Stop() ' Version 2: split on char array. Dim s2 As Stopwatch = Stopwatch.StartNew For i As Integer = 0 To m - 1 Dim result() As String = "cat,frog,dog".Split(New Char() {","c}) If result.Length <> 3 Then Return End If Next s2.Stop() Dim u As Integer = 1000000 Console.WriteLine(((s1.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns")) Console.WriteLine(((s2.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns")) End Sub End Module Output 117.60 ns Split(String()) 97.15 ns Split(Char())
A review. We examined ways to invoke the Split() Function. Split returns a String array that we can use in a For Each loop. We used Split on different characters and strings.For Each, ForStrings
Regex. We called Regex.Split in a more complex pattern example. With Regex, we can split based on patterns and metacharacters. This is more powerful but also more complex.
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