In this post, here is the VB.Net code to count the occurrences of a particular string in a another given string .
Suppose there is a case  where we may want to check whether the string contains particular substring or not. And we may want to count the occurrences of the substring, in that case you can use this method and if count =0, then it means the substring is not found.Below are the 2 codes for the same method, you can use whatever you want.

Method 1 :

    ”’ <summary>
    ”’ Method to Count occurrences of String in Another String
    ”’ </summary>
    ”’ <param name=”inputString”></param>
    ”’ <param name=”searchStr”></param>
    ”’ <param name=”matchCase”>True-MatchCase, False-IgnoreCase</param>
    ”’ <returns></returns>
    Public Function CountOfStrInStr(inputString As String, searchStr As String, matchCase As Boolean) As Integer
        Dim count As Integer = 0, TempLenth AsInteger = 0
        If Not matchCase Then
            inputString = inputString.ToLower()
            searchStr = searchStr.ToLower()
        End If
        ‘getting first occurance
        TempLenth = inputString.IndexOf(searchStr, TempLenth)
        While TempLenth <> -1
            ‘incrementing lenth after finding string
            TempLenth += searchStr.Length
            count += 1
            ‘getting next occurances till loop runs
            TempLenth = inputString.IndexOf(searchStr, TempLenth)
        End While
        Return count
    End Function

Method 2 :

    
    ”’ <summary>
    ”’ Method to Count occurrence in String in Another String using Regex
    ”’ </summary>
    ”’ <param name=”inputString”></param>
    ”’ <param name=”searchStr”></param>
    ”’ <param name=”matchCase”>True-MatchCase, False-IgnoreCase</param>
    ”’ <returns>count of SubString found in string</returns>
    ”’ <remarks>Namespace needed System.Text.RegularExpressions;</remarks>
    Public Function CountOfStrInStr(inputString As String, searchStr As String, MatchCase As Boolean) As Integer
        Dim count As Integer = 0
        If MatchCase Then
            count = Regex.Matches(inputString, searchStr).Count
        Else
            count = Regex.Matches(inputString, searchStr, RegexOptions.IgnoreCase).Count
        End If
        Return count
    End Function