[string] Check if a string contains another string

I want to find if a string contains a ","(comma) in it. Do we have any other option other than reading char-by-char?

There is also the InStrRev function which does the same type of thing, but starts searching from the end of the text to the beginning.

Per @rene's answer...

Dim pos As Integer
pos = InStrRev("find the comma, in the string", ",")

...would still return 15 to pos, but if the string has more than one of the search string, like the word "the", then:

Dim pos As Integer
pos = InStrRev("find the comma, in the string", "the")

...would return 20 to pos, instead of 6.

Building on Rene's answer, you could also write a function that returned either TRUE if the substring was present, or FALSE if it wasn't:

Public Function Contains(strBaseString As String, strSearchTerm As String) As Boolean
'Purpose: Returns TRUE if one string exists within another
On Error GoTo ErrorMessage
    Contains = InStr(strBaseString, strSearchTerm)
Exit Function
ErrorMessage:
MsgBox "The database has generated an error. Please contact the database administrator, quoting the following error message: '" & Err.Description & "'", vbCritical, "Database Error"
End
End Function

You can also use the special word like:

Public Sub Search()
  If "My Big String with, in the middle" Like "*,*" Then
    Debug.Print ("Found ','")
  End If
End Sub

You wouldn't really want to do this given the existing Instr/InstrRev functions but there are times when it is handy to use EVALUATE to return the result of Excel worksheet functions within VBA

Option Explicit

Public Sub test()

    Debug.Print ContainsSubString("bc", "abc,d")

End Sub
Public Function ContainsSubString(ByVal substring As String, ByVal testString As String) As Boolean
    'substring = string to test for; testString = string to search
    ContainsSubString = Evaluate("=ISNUMBER(FIND(" & Chr$(34) & substring & Chr$(34) & ", " & Chr$(34) & testString & Chr$(34) & "))")

End Function