Question

This is a little confusing, why is it like this?

Console.WriteLine(IsNumeric("$0")) - False

Console.WriteLine(IsNumeric("€0")) - False

Console.WriteLine(IsNumeric("£0")) - True

Console.WriteLine(IsNumeric("£")) - False

Seems pretty weird to me, what’s the reason it does this

Edit: works on the end as well:

Console.WriteLine(IsNumeric("300£")) - True

Console.WriteLine(IsNumeric("300£0")) - False

Console.WriteLine(IsNumeric("£300£")) - False

Answer 1

Living in Italy – running on Italian locale

Console.WriteLine(IsNumeric("$0")) ' False
Console.WriteLine(IsNumeric("€0")) ' True
Console.WriteLine(IsNumeric("£0")) ' False
Console.WriteLine(IsNumeric("£"))  ' False

while this will give you back always true

using System.Globalization;

Console.WriteLine(MyIsNumeric("$0", NumberStyles.AllowCurrencySymbol, "en-US"))
Console.WriteLine(MyIsNumeric("€0", NumberStyles.AllowCurrencySymbol, "it-IT")) 
Console.WriteLine(MyIsNumeric("£0", NumberStyles.AllowCurrencySymbol, "en-GB")) 


Public Function MyIsNumeric(ByVal val as String, ByVal NumberStyle as NumberStyles, cName as String) as Boolean
    Dim result as Double
    return Double.TryParse(val,NumberStyle, new CultureInfo(cName), result)
 End Function

So we could conclude that IsNumeric (originally defined in VB6 runtime) is smart enough to exclude from its parsing the current locale currency symbols if they precede or follow the input string.