Create a function that separates the characters of a word by symbols - vb.net

Question

I want to create a function where, for example, if I put the word visual in the input box I have to select from the ComboBox one of these 3 symbols: space, . , or *, in the output box I want the result of the word visual to come out like this: v.i.s.u.a.l or v i s u a l
I already know how to output a result that separates the string by a space but I don't know how to do it using a ComboBox with 3 symbols
This is the code I used for separating with a space
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim n As Integer
Dim str As String = "mis programing II"
Dim str2 As String = ""
Dim cc As String
For i = 1 To Len(str)
cc = Mid(str, i, 1)
str2 = str2 & cc & " "
Next
MsgBox(str2)
End Sub
End Class

Answer 1

You can use String.Join like this:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim str As String = "mis programing II"
Dim str2 As String = String.Join(str.ToCharArray(), ComboBox1.Text)
MsgBox(str2)
End Sub
I assumed the seperator has been selected in the ComboBox. Else, replace ComboBox1.Text with the seperator you want to use.
Update
Thanks to #JQSOFT, I just confirmed that String.Join does not work on Char arrays. Well here's another solution.
Dim str As String = "mis programing II"
Dim listX As New List(Of String)
Dim act As Action(Of Char) = Sub(c) listX.Add(CStr(c))
For Each c As Char In str.ToCharArray()
act.Invoke(c)
Next
Dim str2 As String = String.Join(".", listX.ToArray)
Console.WriteLine(str2)

Answer 2

Nice exercise:
Can be done using LINQ as follows:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim str As String = txtInput.Text '"mis programing II" for this example..
Dim sep As Char
'Validate your inputs:
If String.IsNullOrWhiteSpace(str) OrElse
Not Char.TryParse(cmbSep.Text, sep) Then
Return
End If
'and in one line:
Dim str2 = String.Join("", str.Split(" "c).
SelectMany(Function(x) x.ToCharArray.Append(" "c)).
Select(Function(x) $"{x}{If(Char.IsWhiteSpace(x), " ", sep)}")).
Replace($"{sep} ", " ").Trim
MessageBox.Show(str2)
End Sub
If you are not allowed to use LINQ, then the next snippet will do the same:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim str As String = txtInput.Text '"mis programing II" for this example..
Dim sep As Char
'Validate your inputs:
If String.IsNullOrWhiteSpace(str) OrElse
Not Char.TryParse(cmbSep.Text, sep) Then
Return
End If
Dim str2 As New StringBuilder
For Each word In str.Split(" "c)
For i = 0 To word.Length - 2
str2.Append(word(i)).Append(sep)
Next
str2.Append(word(word.Length - 1)).Append(" ")
Next
MessageBox.Show(str2.ToString.Trim)
End Sub
Some outputs:
m.i.s p.r.o.g.r.a.m.i.n.g I.I
m^i^s p^r^o^g^r^a^m^i^n^g I^I
m*i*s p*r*o*g*r*a*m*i*n*g I*I
m-i-s p-r-o-g-r-a-m-i-n-g I-I
m_i_s p_r_o_g_r_a_m_i_n_g I_I
m i s p r o g r a m i n g I I