Let me try to explain how number work in the .NET Framework.
Numbers are internally represented in the same way in the memory no matter which culture you use. Our Bulgarian decimal separator is the same as yours, i.e. a comma. The American style uses a dot. But the important thing is that once the string is parsed regardless of the culture, the actual Decimal value that is obtained has the same byte representation in memory.
So, since the .NET Framework does not offer the functionality that you require out-of-the-box, you will have to develop your own code to handle the two different decimal separators.
One possible way to do this would be to create a custom cell editor, that will be some kind of a smart TextBox, which will accepts numbers typed with a comma and with a dot and regardless of the symbol used convert them to the desired decimal value.
Here you can learn more about creating custom cell editors. So basically, your magic textbox editor will accept string with any kind of possible decimal separator and convert them to the correct Decimal value. The implementation of such a control is beyond the scope of Telerik support.
I hope this helps.
the Telerik team
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