Find And Format String in RichTextBox Vb.NET - vb.net

Question

I am working with Vb.NET and the requirement was to find the string n RTF control and make it , bold,italic or whatever color,I have done my efforts to find the string but yesterday I found it not working as per my requirement.
At bottom I will write the full code with test data.
I have a simple form and two control on it, One is CombBox to Select Different Test Cases and One RichTextBox for Displaying the Text.
'Class Declarations
Private FormattingApplied As Boolean = False
Private SelectedBold As Boolean = False
Private SearchText As String = String.Empty
Private SelectedItalic As Boolean = False
Private SelectedUnderLine As Boolean = False
' On Form Load
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
cmbList.Items.Add("Apple Pina Apple")
cmbList.Items.Add("Apple Delicious Pineapple")
cmbList.Items.Add("Apple Milk Shake Apa")
cmbList.Items.Add("Apple Strawberry ")
FormattingApplied = True
SelectedBold = True
cmbList.SelectedIndex = 0
End Sub
Function UppercaseFirstLetter(ByVal val As String) As String
' Test for nothing or empty.
If String.IsNullOrEmpty(val) Then
Return val
End If
Dim array() As Char = val.ToCharArray
array(0) = Char.ToUpper(array(0))
Return New String(array)
End Function
Private Sub ApplyFormatting(ByVal SearchText As String)
Dim TrimmedString As String = String.Empty
Dim ISTrimmed As Boolean = False
If FormattingApplied Then
Dim count As New List(Of Integer)()
If rtfText.Text.Length >= 53 Then
rtfText.Text = rtfText.Text.Substring(0, 50) + "..."
End If
For i As Integer = 0 To rtfText.Text.Length - 1
If rtfText.Text.IndexOf(SearchText, i) <> -1 Then
count.Add(rtfText.Text.IndexOf(SearchText, i))
ElseIf rtfText.Text.IndexOf(UppercaseFirstLetter(SearchText), i) <> -1 Then
count.Add(rtfText.Text.IndexOf(UppercaseFirstLetter(SearchText), i))
End If
Next
Try
For i As Integer = 0 To count.Count - 1
rtfText.[Select](count(i), SearchText.Length)
If SelectedBold Then
rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Bold)
ElseIf SelectedItalic Then
rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Italic)
ElseIf SelectedUnderLine Then
rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Underline)
'ElseIf SelectedBold AndAlso SelectedItalic AndAlso SelectedUnderLine Then
' rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Underline)
End If
count.RemoveAt(i)
Next
'For i As Integer = 0 To count.Count - 1
' rtfText.[Select](count(i), SearchText.Length)
' If SelectedBold Then
' rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Bold)
' ElseIf SelectedItalic Then
' rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Italic)
' ElseIf SelectedUnderLine Then
' rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Underline)
' End If
' count.RemoveAt(i)
'Next
Catch
count.Reverse()
End Try
rtfText.[Select](rtfText.Text.Length, 0)
rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Regular)
End If
End Sub
Private Sub cmbList_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbList.SelectedIndexChanged
rtfText.Text = cmbList.SelectedItem.ToString()
rtfText.[Select](0, rtfText.Text.Length)
rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Regular)
If cmbList.SelectedIndex > -1 Then
ApplyFormatting("apple")
End If
End Sub
Here is the output:

Answer 1

Use this method
Private Sub formatString(ByVal SearchText As String)
Dim position As Integer = 0
Dim rtfString As String = LCase(rtfText.Text)
Dim cnt As Integer = 0
Dim isStop As Boolean = False
While Not isStop
Dim i As Integer = rtfString.IndexOf(SearchText, cnt)
If i < 0 Then
isStop = True
Else
rtfText.Select(i, SearchText.Length)
rtfText.SelectionFont = New Font(rtfText.Font, FontStyle.Bold)
cnt = i + 1
End If
End While
rtfText.Select(position, 0)
End Sub
in the cmbList_SelectedIndexChanged
If cmbList.SelectedIndex > -1 Then
'ApplyFormatting("apple")
formatString("apple")
End If