如何根据当前文化正确转换Double和DateTime？

Hi in my excel like application i want to convert many values and validate it. But while converting double and dateTime i facing some serious issues. The below code snippet is working well for English Culture. But when the culture is German i get the text as 24.3.2014. Now it is converted into double and returns a double value but i don't want it to be converted to double. Any suggestion on it.?Hi in my excel like application i want to conve