How do you replace the last occurance of a , with the word "and"? - vb.net

Question

How do you replace the last occurance of a , with the word and? Can you please give me an idea?
i have 3 checkboxes, 1 rich textbox
to display the output, 1 button
(Aparri) or (Camalanuigan) or (Lallo)
Cagayan(Aparri, Camalanuigan) or Cagayan(Aparri,Camalanuigan,Lallo)
I would like the output to be like this: #Cagayan(Aparri and Camalanuigan) or #Cagayan(Aparri,Camalanuigan And Lallo)
this is my code:
Dim rws As String
If Aparri.Checked = True Then
close_parenthesis.Checked = True
If rws = "" Then
rws = "(" + Aparri.Text
End If
End If
If Aparri.Checked = False Then
rws = ""
End If
If Camalanuigan.Checked = True Then
close_parenthesis.Checked = True
If rws = "" Then
rws = "(" + Camalanuigan.Text
Else
rws = rws & ", " & Camalanuigan.Text
End If
End If
If Lallo.Checked = True Then
close_parenthesis.Checked = True
If rws = "" Then
rws = "(" + Lallo.Text
Else
rws = rws & ", " & Lallo.Text
End If
End If
If close_parenthesis.Checked = True Then
If rws = "" Then
Else
rws = rws + close_parenthesis.Text
End If
End If
Display.Text = rws.ToString
Output: (Aparri,Camalanuigan,Lallo)
i want the out like this (Aparri,Camalanuigan and Lallo)

Answer 1

Here, I haven't even seen your code but I get what you want to do by looking at the picture. It can be done in shorter version but I have explained what's going on in each and every line so it's lengthy.
I have written this code:
'let's say the string is "Aparri, Camalanuigan, Lallo" . that's what your code does, right?
dim Strng as string = "Aparri, Camalanuigan, Lallo"
'now find the position of last appearing ","
Dim comaposition As Integer
comaposition = Strng.LastIndexOf(",") 'it is zero based
'if not found, it will return -1 and u can exit, no need to do the work
if commaposition = "-1" then
exit sub
end if
'remove the comma
Dim String_After_Removing_Comma As String
String_After_Removing_Comma = Strng.Remove(comaposition, 1)
'add "and" in the same position where comma was found
Dim final_string As String
final_string = String_After_Removing_Comma.Insert(comaposition, " and")
'show it on the textbox
DisplayTxt.Text = final_string
You can do this thing after finding your final string (rws in your code).
Hope this helps

Answer 2

You can use the following function to replace last occurrence.
Public Function ReplaceLastOccurrence(ByVal source As String, ByVal searchText As String, ByVal replace As String) As String
Dim position = source.LastIndexOf(searchText)
If (position = -1) Then Return source
Dim result = source.Remove(position, searchText.Length).Insert(position, replace)
Return result
End Function
and you use display text as
Display.Text = ReplaceLastOccurence(rws, ",", "and")
in your last line of code

Answer 3

You always can do it by yourself with single loop and knowledge about last index
' Create array of selected strings
Dim selectedTexts =
New List(Of CheckBox) From { Aparri, Camalanuigan, Lallo }.
Where(Function(checkbox) checkbox.Checked).
Select(Function(checkbox) checkbox.Text).
ToArray()
' Separate selected strings by delimeters
Dim lastIndex = selectedTexts.GetUpperBound(0)
Dim builder = New StringBuilder()
For i As Integer = 0 To lastIndex
If i > 0 Then
Dim delimeter = If(lastIndex > 0 AndAlso lastIndex = i, " and ", ", ")
builder.Append(delimeter)
End If
builder.Append(test(i))
Next
' Wrap with parenthesis if result not empty
If builder.Length > 0 Then
builder.Insert(0, "(")
Dim close = If(close_parenthesis.Checked, close_parenthesis.Text, "")
builder.Append(close)
End If
' Print result
Display.Text = builder.ToString()