Fraction To Decimal

I wrote a simple vb.net code to convert from Fraction to decimal easily:

Private Function FractionToDecimal(ByVal frac As String) As String
      Dim decimalVal As String = "0"
      Dim upper As Decimal = 0
      Dim lower As Decimal = 0
      Dim remain As Decimal = 0
      If frac.IndexOf("/") <> -1 Then


          If frac.IndexOf(" ") <> -1 Then
              remain = CType(frac.Substring(0, frac.IndexOf(" ")), Decimal)
              frac = frac.Substring(frac.IndexOf(" "))
          End If

          upper = CType(frac.Substring(0, frac.IndexOf("/")), Decimal)
          lower = CType(frac.Substring(frac.IndexOf("/") + 1), Decimal)

          decimalVal = (remain + (upper / lower)).ToString
      End If
      Return decimalVal
  End Function