Problem with simple expression

Question

Hi,
I have an SSRS report based on a SSAS cube that contains a Date field called Closing_Date.
This field can be null in the database.
The purpose is to convert the DateTime into a Date field respecting the user's locale
This expresion returns a blank for empty dates and a DateTime (yyyy/mm/dd hh:mm:ss) for non empty dates
=Fields!Closing_Date.Value,DateFormat.ShortDate
This expression returns OK for non empty dates and NOK for empty dates
=IIF(Trim(Cstr(Fields!Closing_Date.Value)) <> "","OK","NOK")
However this expression returns an #error for all empty dates. I don't understand because he should just return NOK.
Why would a change in the True part if the IIF give a different result if the date is empty.
=IIF(Trim(Cstr(Fields!Closing_Date.Value)) <> "",FormatDateTime(Fields!Closing_Date.Value,DateFormat.ShortDate),"NOK")
I get this error in the VS.Net Conversion from string "" to type 'Date' is not valid
Any Idea's?
PS : Other date fields (that don't contain null's) work correctly and can be converted with FormatDateTime function
Regards,
Sven Peeters

Answer 1

Hi Sven,
According to your description, when you iif function to set empty dates to NOK when you preview the report, the error occurred: Conversion from string "" to type 'Date' is not valid. But the fields with data can be converted successfully.
I reproduced the issue in my local machine, the error is caused by data type. I suppose the data type of Closing_Date is string, so when we tried to convert a string with null data, the error occurred. To achieve your goal, please use the expression like
below:
=IIF(Fields!Closing_Date.Value = "", "NOK" , FormatDateTime(IIf(Fields!Closing_Date.Value = "" , Nothing , Fields!Closing_Date.Value) , DateFormat.ShortDate))
If you have any more questions, please feel free to ask.
Thanks,
Wendy Fu