how to find the number of occurrences of a substring within a string vb.net

Question

I have a string (for example: \"Hello there. My name is John. I work very hard. Hello there!\") and I am trying to find the number of occurrences of the string

Answer 1

You could create a recursive function using IndexOf. Passing the string to be searched and the string to locate, each recursion increments a Counter and sets the StartIndex to +1 the last found index, until the search string is no longer found. Function will require optional parameters Starting Position and Counter passed by reference:

Function InStrCount(ByVal SourceString As String, _
                    ByVal SearchString As String, _
                    Optional ByRef StartPos As Integer = 0, _
                    Optional ByRef Count As Integer = 0) As Integer
    If SourceString.IndexOf(SearchString, StartPos) > -1 Then
        Count += 1
        InStrCount(SourceString, _
                   SearchString, _
                   SourceString.IndexOf(SearchString, StartPos) + 1, _
                   Count)
    End If
    Return Count
End Function

Call function by passing string to search and string to locate and, optionally, start position:

Dim input As String = "Hello there. My name is John. I work very hard. Hello there!"
Dim phrase As String = "hello there"
Dim Occurrences As Integer

Occurrances = InStrCount(input.ToLower, phrase.ToLower)

Note the use of .ToLower, which is used to ignore case in your comparison. Do not include this directive if you do wish comparison to be case specific.