vb.net - Unexpected Decimal Separator Behavior with CultureInfo in .NET - Stack Overflow

In the attached images, you can observe that I am explicitly using both InvariantCulture and a new instance of CultureInfo("en-US") when converting a Double to a String:

value.ToString(Globalization.CultureInfo.InvariantCulture)
value.ToString(New Globalization.CultureInfo("en-US"))

Given these calls, the expected result should be the string "-807.7935669463161", where the decimal separator is a period (.). However, the output uses the comma (","), which matches the decimal separator of my system's regional settings.

I know how to implement a workaround, but why is the expected behavior not being respected?

If s <> value.ToString(us) Then
    Console.WriteLine($"Original value: {value}")
    Dim sFormatted As String =
        value.ToString(Globalization.CultureInfo.InvariantCulture)
    ' Should display "-807.7935669463161" :
    Console.WriteLine("sFormatted: " + sFormatted)
    ' Should display "-807.7935669463161" :
    Console.WriteLine("en-US Culture" +
             value.ToString(New Globalization.CultureInfo("en-US")))
    _usedVariables(s).Add(sFormatted)
End If

You may download the whole solution at here

****** EDIT ********* I have found what was happening. If you look at the following you will see that the last argument is a double, while the signature expects a String. But there is no error message and the code compiles and runs. So, this is because there is no Option Strict On declaration.

Dim us As New System.Globalization.CultureInfo("en-US")
Dim _usedVariables As New Dictionary(Of String, List(Of String))

Sub Main(args As String())
    Dim value As Double = 30
    Dim termValue As Double = 1.25
    Dim exponent As Double = value
    value = Math.Pow(termValue, value)
    AddToUsedVars(termValue.ToString(us) + "^" + exponent.ToString(us), -value)
End Sub

Public Sub AddToUsedVars(s As String, value As String)
    If Regex.IsMatch(s, "^\([^()]+\)") Then
        s = s.Substring(1, s.Length - 2)
    End If
    If Not _usedVariables.ContainsKey(s) Then
        _usedVariables.Add(s, New List(Of String))
    End If
    If s <> value.ToString(us) Then
        Console.WriteLine($"Original value: {value}")
        Dim sFormatted As String =
            value.ToString(Globalization.CultureInfo.InvariantCulture)
        ' Should display "-807.7935669463161" :
        Console.WriteLine("sFormatted: " + sFormatted)
        ' Should display "-807.7935669463161" :
        Console.WriteLine("en-US Culture" +
                 value.ToString(New Globalization.CultureInfo("en-US")))
        _usedVariables(s).Add(sFormatted)
    End If
End Sub

In the attached images, you can observe that I am explicitly using both InvariantCulture and a new instance of CultureInfo("en-US") when converting a Double to a String:

value.ToString(Globalization.CultureInfo.InvariantCulture)
value.ToString(New Globalization.CultureInfo("en-US"))

Given these calls, the expected result should be the string "-807.7935669463161", where the decimal separator is a period (.). However, the output uses the comma (","), which matches the decimal separator of my system's regional settings.

I know how to implement a workaround, but why is the expected behavior not being respected?

If s <> value.ToString(us) Then
    Console.WriteLine($"Original value: {value}")
    Dim sFormatted As String =
        value.ToString(Globalization.CultureInfo.InvariantCulture)
    ' Should display "-807.7935669463161" :
    Console.WriteLine("sFormatted: " + sFormatted)
    ' Should display "-807.7935669463161" :
    Console.WriteLine("en-US Culture" +
             value.ToString(New Globalization.CultureInfo("en-US")))
    _usedVariables(s).Add(sFormatted)
End If

You may download the whole solution at here

****** EDIT ********* I have found what was happening. If you look at the following you will see that the last argument is a double, while the signature expects a String. But there is no error message and the code compiles and runs. So, this is because there is no Option Strict On declaration.

Dim us As New System.Globalization.CultureInfo("en-US")
Dim _usedVariables As New Dictionary(Of String, List(Of String))

Sub Main(args As String())
    Dim value As Double = 30
    Dim termValue As Double = 1.25
    Dim exponent As Double = value
    value = Math.Pow(termValue, value)
    AddToUsedVars(termValue.ToString(us) + "^" + exponent.ToString(us), -value)
End Sub

Public Sub AddToUsedVars(s As String, value As String)
    If Regex.IsMatch(s, "^\([^()]+\)") Then
        s = s.Substring(1, s.Length - 2)
    End If
    If Not _usedVariables.ContainsKey(s) Then
        _usedVariables.Add(s, New List(Of String))
    End If
    If s <> value.ToString(us) Then
        Console.WriteLine($"Original value: {value}")
        Dim sFormatted As String =
            value.ToString(Globalization.CultureInfo.InvariantCulture)
        ' Should display "-807.7935669463161" :
        Console.WriteLine("sFormatted: " + sFormatted)
        ' Should display "-807.7935669463161" :
        Console.WriteLine("en-US Culture" +
                 value.ToString(New Globalization.CultureInfo("en-US")))
        _usedVariables(s).Add(sFormatted)
    End If
End Sub

• vb.net
• decimal
• separator

Share Improve this question Follow edited Feb 4 at 17:10 Olivier Jacot-Descombes 113k1414 gold badges147147 silver badges198198 bronze badges asked Feb 4 at 14:24 Xavier JunquéXavier Junqué 48444 silver badges88 bronze badges 12

• 1 meta.stackoverflow.com/questions/285551/… Please Include Code as Text not images – Richard Commented Feb 4 at 14:28
• @Richard, I am sorry and I have edited and included the code. – Xavier Junqué Commented Feb 4 at 14:32
• Please include a minimal reproducible example (stackoverflow.com/help/minimal-reproducible-example): this will at least show what type value is. – Richard Commented Feb 4 at 14:33
• @Richard. Now, you may download the whole solution. The problem is arising in Module Term, at lines 192-198. – Xavier Junqué Commented Feb 4 at 14:52
• 2 @XavierJunqué Now you know why Option Strict On is a really good idea ;) Also, the string concatenation operator in VB.NET is &, not +. – Andrew Morton Commented Feb 4 at 16:01

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1 Answer 1

Sorted by: Reset to default 2

In the Sub AddToUsedVars you have a parameter value As String. Then you try to format it with value.ToString(<some culture info>). But this does not work, because value is already a String. It is not a Double. Change the parameter to value As Double, then your formats will work.

During formatting, the string is not perceived as a number and therefore no numeric formats are applied to it.

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This happened because Option Strict was Off. in Visual Studio you can set the defaults for new VB projects and solutions in the menu Tools > Options:

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For a specific project, you can set this option in the project properties, so that it applies to all project files where this option was not set explicitly: