For example the following culture:

 this.currency.Culture = new System.Globalization.CultureInfo("prs-AF"); has     

this.currency.Culture.NumberFormat

{System.Globalization.NumberFormatInfo}
    CurrencyDecimalDigits: 2
===>  CurrencyDecimalSeparator: "."
===>  CurrencyGroupSeparator: ","
    CurrencyGroupSizes: {int[1]}
    CurrencyNegativePattern: 3
    CurrencyPositivePattern: 0
    CurrencySymbol: "؋"
    DigitSubstitution: NativeNational
    IsReadOnly: false
    NaNSymbol: "ناعدد"
    NativeDigits: {string[10]}
    NegativeInfinitySymbol: "-∞"
    NegativeSign: "-"
    NumberDecimalDigits: 2
===>  NumberDecimalSeparator: ","
===>  NumberGroupSeparator: "."
    NumberGroupSizes: {int[1]}
    NumberNegativePattern: 3
    PerMilleSymbol: "‰"
    PercentDecimalDigits: 2
    PercentDecimalSeparator: ","
    PercentGroupSeparator: "."
    PercentGroupSizes: {int[1]}
    PercentNegativePattern: 1
    PercentPositivePattern: 1
    PercentSymbol: "%"
    PositiveInfinitySymbol: "∞"
    PositiveSign: "+"

Typing 12345 in the control produces Value 123 which is wrong. Parsing becomes wrong after the group separator kicks in.