Put a space in front of every capital letter in a string - string

Question

I want to put spaces before each capital letter in a string.
So turn this: TheQuickBrownFox
into this: The Quick Brown Fox
This is the code I have so far: it finds uppercase chars in the string and shows each upper letter in a Message Box.
I can't figure out where to go from here:
Dim input As String = "TheQuickBrownFox"
For i As Integer = 0 To input.Length - 1
Dim c As Char = input(i)
If Char.IsUpper(c) Then
MsgBox(c)
End If
Next
I've googled around but I wasn't able to find a solution for visual basic.

Answer 1

A couple of example using LINQ:
Imports System.Linq
Imports System.Text
Dim input As String = "TheQuickBrownFox"
In case you don't know it, a String is a collection of Chars, so you can iterate the string content using a ForEach loop (e.g., For Each c As Char In input).
▶ Generate a string from an collection of chars (Enumerable(Of Char)), excluding the first uppercase char if it's the first in the string.
The second parameter of a Select() method, when specified (in Select(Function(c, i) ...)), represents the index of the element currently processed.
String.Concat() rebuilds a string from the Enumerable(Of Char) that the Select() method generates:
Dim result = String.Concat(input.Select(Function(c, i) If(i > 0 AndAlso Char.IsUpper(c), ChrW(32) + c, c)))
The same, not considering the position of the first uppercase char:
Dim result = String.Concat(input.Select(Function(c) If(Char.IsUpper(c), ChrW(32) + c, c)))
▶ With an aggregation function that uses a StringBuilder as accumulator (still considering the position of the first uppercase char).
When processing strings, a StringBuilder used as storage can make the code more efficient (creates way less garbage) and more performant.
See, e.g., here: How come for loops in C# are so slow when concatenating strings?
➨ Note that I'm adding an Array of chars to the StringBuilder:
Dim result = input.Aggregate(New StringBuilder(),
Function(sb, c) sb.Append(If(sb.Length > 0 AndAlso Char.IsUpper(c), {ChrW(32), c}, {c})))
➨ result is a StringBuilder object: extract the string with result.ToString().
Or, as before, without considering the position:
Dim result = input.Aggregate(New StringBuilder(),
Function(sb, c) sb.Append(If(Char.IsUpper(c), {ChrW(32), c}, {c})))
▶ The two example above are somewhat equivalent to a simple loop that iterates all chars in the string and either creates a new string or uses a StringBuilder as storage:
Dim sb As New StringBuilder()
For Each c As Char In input
sb.Append(If(sb.Length > 0 AndAlso Char.IsUpper(c), {ChrW(32), c}, {c}))
Next
Change the code as described before if you want to add a space to the first uppercase Char without considering its position.

Answer 2

Yet another option is a language extension method.
Imports System.Text.RegularExpressions
Module Module1
Sub Main()
Demo()
Console.ReadLine()
End Sub
Private Sub Demo()
Dim data = New List(Of String) From
{
"ThisIsASentence",
"TheQuickBrownFox",
"ApplesOrangesGrapes"}
data.ForEach(Sub(item) Console.WriteLine($"{item,-25}[{item.SplitCamelCase}]"))
End Sub
End Module
Public Module StringExtensions
<Runtime.CompilerServices.Extension>
Public Function SplitCamelCase(sender As String) As String
Return Regex.Replace(Regex.Replace(sender,
"(\P{Ll})(\P{Ll}\p{Ll})", "$1 $2"),
"(\p{Ll})(\P{Ll})",
"$1 $2")
End Function
End Module

Answer 3

You can use a regular expression:
Dim input = "TheQuickBrownFox"
Dim withSpaces = Regex.Replace(a, "(?<!^)([A-Z])", " $1")
The regex finds any uppercase A-Z that are not preceded by the start of the string and captures it into a group. The replacement takes the group content and prefixes a space
If you don't want to use the negative lookbehind, you can trim the result:
Dim withSpaces = Regex.Replace(a, "([A-Z])", " $1").TrimStart()
Or don't trim if you don't care that the string starts with a space

Answer 4

To expand on your code:
Dim input As String = "TheQuickBrownFox"
Dim outputSB as new StringBuilder
For i As Integer = 0 To input.Length - 1
Dim c As Char = input(i)
If Char.IsUpper(c) Then
outputSB.Append(" ")
'MsgBox(c)
End If
outputSB.Append(c)
Next
Console.Writeline(outputSB.ToString())