Find all instances of a word in a string and display them in textbox (vb.net) - vb.net

Question

I have a string filled with the contents of a textbox (pretty large).
I want to search through it and display all occurances of this word. In addition I need the searchresult to display some charachters in the string before and after the actual searchterm to get the context for the word.
The code below is part of a code that takes keywords from a listbox one by one using For Each. The code displays the first occurance of a word together with the characters in front and after the word - and stop there. It will also display "no Match for: searched word" if not found.
As stated in the subject of this question - I need it to search the whole string and display all matches for a particular word together with the surrounding characters.
Where = InStr(txtScrape.Text, Search)
If Where <> 0 Then
txtScrape.Focus()
txtScrape.SelectionStart = Where - 10
txtScrape.SelectionLength = Where + 50
Result = txtScrape.SelectedText
AllResults = AllResults + Result
Else
AllResults = AllResults + "No Match for: " & item
End If

Answer 1

I recommend that you can split the string into long sentences by special symbols, such as , : ? .
Split(Char[])
You can refer to the following code.
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
RichTextBox1.Text = ""
Dim Index As Integer
Dim longStr() As String
Dim str = TextBox3.Text
longStr = TextBox1.Text.Split(New Char() {CChar(":"), CChar(","), CChar("."), CChar("?"), CChar("!")})
Index = 0
For Each TheStr In longStr
If TheStr.Contains(str) Then
RichTextBox1.AppendText(longStr(Index) & vbCrLf)
End If
Index = Index + 1
Next
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
TextBox1.Text = "....."
End Sub
End Class
Result:

Answer 2

Try like this:
Dim ArrStr() As String
Dim Index As Integer
Dim TheStr As String
Dim MatchFound As Boolean
MatchFound = False
ArrStr = Split(txtScrape.text," ")
Index = 1
For Each TheStr In ArrStr
If TheStr = Search Then
Console.WriteLine(Index)
MatchFound = True
End If
Index = Index + 1
Next
Console.WriteLine(MatchFound)
Inside the If statement you will get the index there. And MatchFound is the Boolean value if match found.