String Replace Examples
This page was last reviewed on Nov 10, 2023.
Dot Net Perls
Replace. This VB.NET function changes the contents of a String. It makes all instances of one substring become another substring.
Function details. It is important to know some of this Function's details. Replace() cannot handle patterns or regular expressions. It can cause performance problems.
First example. Here we call Replace. Its parameters can be literal strings or dynamic ones determined at runtime. We replace the first parameter with the second parameter.
Argument 1 The first argument we pass to the Replace Function is the substring we want to change to something else.
Argument 2 This is the string we want to have in the result—the replacement value. This may be found in the result of Replace.
Module Module1 Sub Main() ' Replace substring with another substring. Dim value1 As String = "abcdef" Dim value2 As String = value1.Replace("abc", "hi") Console.WriteLine(value1) Console.WriteLine(value2) End Sub End Module
abcdef hidef
Every instance. Replace() will internally loop through the entire source string. It replaces all occurrences of the substring you want to replace.
Tip This behavior is useful when dealing with common string replacements in programs.
But If you do not understand this behavior you may end up writing inefficient code that has unneeded loops.
Here The string containing the characters "Net" is replaced with the characters "Bottle." These substrings are case-sensitive.
Module Module1 Sub Main() ' Assign string to literal constant. Dim value1 As String = "Dot Net Perls is about Dot Net." Console.WriteLine(value1) ' Replace every instance of the string. Dim value2 As String = value1.Replace("Net", "Bottle") Console.WriteLine(value2) End Sub End Module
Dot Net Perls is about Dot Net. Dot Bottle Perls is about Dot Bottle.
Remove all substrings. We can use Replace() to remove all substrings from a string. A new copy of the string, with all matching substrings removed, is returned.
Important A zero-length string (the empty string literal) is still a string, so we can replace substrings with it.
Detail We can use an empty string literal or the Nothing literal to indicate an empty string.
Module Module1 Sub Main() Dim value As String = "cat Remove dog Remove bird" ' We can use Replace to remove all instances of a substring. Dim result As String = value.Replace("Remove", "") Console.WriteLine("BEFORE: " + value) Console.WriteLine("AFTER: " + result) End Sub End Module
BEFORE: cat Remove dog Remove bird AFTER: cat dog bird
StringBuilder. This class has a Replace() that functions the same way as the String method. It has parameters that indicate the before and after substrings.
However The StringBuilder class implements optimizations that can improve memory usage and speed when doing many replacements.
Imports System.Text Module Module1 Sub Main() ' Create new StringBuilder and initialize it. Dim builder As New StringBuilder("This is an example.") Console.WriteLine(builder) ' Replace string in StringBuilder. builder.Replace("This", "Here") Console.WriteLine(builder) ' Insert into StringBuilder. builder.Insert(0, "Sentence: ") Console.WriteLine(builder) End Sub End Module
This is an example. Here is an example. Sentence: Here is an example.
Summary. The Replace function on String will allocate an entire new string. It will replace all instances of the first parameter with the second parameter.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Nov 10, 2023 (simplify).
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