Check condition with space i.e empty value

Hi Friends,
Currently in my scenario i have to calculate Processing amount,sometime its in double i.e 2587.25 and sometime its space i.e empty.
now i have to check whether its greater than zero if yes then process further.
I am using like this:-
convert.todouble(ProcessingAmount)>0 — this works in double value but not in space or empty value. (error:- Input string is not in correct format)
How to use above condition.kindly help me over this.

To check the empty condition you can 1st check
String.isEmptyOrNull(variable name)
If it is true that means variable contains value. Afterwards you can convert it into double


Check length of the string before processing.

amountLength = ProcessingAmount.Tostring.Length

If amountLength > 0
Then do further steps

I am using like this:-
convert.ToDouble(ProcessingAmount)>0 Or string.IsNullOrEmpty(ProcessingAmount)
but it not works