CDec doesn't return the correct value - vb.net

Question

I make code that multiply all values of a DatagridView column. The code is working, but there's a problem. In particular, I've added this:
Return CDec(x.Cells("Quote").Value.ToString.Replace(",", "."))
That returns me the split value, for example, if I would have:
2,7 the correct value to return is: 2.7, but the code returns 27 and this is strange. I performed some trying, and if I delete the CDec like:
Return x.Cells("Quote").Value.ToString.Replace(",", ".")
The value returned is correct, but I've a contrast with this function:
Private Function MultiplyDecimals(ByVal sender As Decimal()) As Decimal
Dim Result As Decimal
If Not sender Is Nothing AndAlso Not sender.Length = 0 Then
Result = sender.Aggregate(Function(a, b) a * b)
End If
Return Result
End Function
That returns me 0 if I delete "As Decimal". So what's wrong?
UPDATE with possible solution:
Dim bles = x.Cells("Quote").Value.ToString.Replace(",", ".")
Dim key = Convert.ToDecimal(bles)
MessageBox.Show(key)
Return CDec(key)

Answer 1

Since it looks like you are also trying to manually convert from a different culture, you should use the .NET methods for this, rather than roll your own. You have two conversions going on: From one cultural number system to another and from string to a numeric type.
To convert a string like "2,7" which might be a French or Italian value:
Dim str As String = "2,7"
Dim decVal As Decimal
If Decimal.TryParse(str, NumberStyles.AllowDecimalPoint,
New CultureInfo("it-IT"), decVal) Then
' decVal has the value
Else
' Parse failed
End If
or:
Dim cult As New CultureInfo("fr-FR")
If Decimal.TryParse(str, NumberStyles.AllowDecimalPoint,
cult, decVal) Then ...
This can often work, but you might get an exception depending on the content:
Dim decVal As Decimal
Dim cult As New CultureInfo("fr-FR")
decVal = Convert.ToDecimal(str, cult)
Console.WriteLine(decVal.ToString)
Note: I am guessing at the culture of the data. Based on your recent, related question Google indicates "Nazione" is Italian, but data from/about Algeria might well be French Algerian.
CDec, like most of the legacy VB functions, is only equipped to work with the active culture settings. So, it will seem like it is "broken" in some cases:
Console.WriteLine(CDec("2.7")) ' --> 2.7D US/Can
Console.WriteLine(CDec("2,7")) ' --> 27D
Console.WriteLine(CDec("2,,7")) ' --> 27D
On a machine using French or Italian culture, the opposite will happen: "2.7" will come out 27, "2,7" to 2.7D, but "2,,7" will probably crash just like "2..7" would in the US/Can.
The reason for this behavior is that in US/Can, a comma looks like noise and CDec ignores it. A string with a single decimal-dot will convert, but a string with 2 is invalid. It would be the reverse for French where the comma is used: any number of dots look like noise, and only single decimal-comma format will parse.
It is all part of the reason no one included CDec in the solution: It is sub-optimal for any sort of cultural conversions. Manually removing or replacing decimal markers is even less optimal when there are methods designed to do that only when needed.

Answer 2

Since you have a string value, try Decimal.Parse() instead of CDec().
If that doesn't give you the result you expect, then either you're not handling the string that you think you are (in which case, try logging the exact string to a text file or similar so you can see exactly what you have), or the PC's culture settings are not what you think they are (it may be set to a culture that uses the comma, rather than a period, as the decimal separator), in which case try one of the Decimal.Parse() overloads that allows you to specify the culture, or perhaps even just remove the call to .Replace().