Can't Add Unknown Error

M

MadhuG001

Member
Hi All,
My data set is Students marks & requirement is to get the total mark & percentage of each student.
So I have moved my data from a collection to Work Queue("Add to Queue" then I have used "Get Next Item")

Then to get the total mark of an individual student, I have used a Calculation Stage.
Where I kept: [Data.English]+[Data.Hindi]+[Data.Math]
Data is the Collection name, which stores marks of individual students.

But I am getting an error as:- Can't add to Unknown

Please advise, what correction need to do.

Thank You.
 
G

gil.silva

Active Member
Hello Madhu,

In the past, I got the same error as you, but with concatenating text, it seems just another Blue Prism bug.
I solved it adding an empty string between the data items. In your case, please try to add 0 between the data items.
Expression: [Data.English]+ 0 + [Data.Hindi]+ 0 + [Data.Math]
 
N

nthnhwrdprm

New Member
I know this is an old post, but ran across it when searching for a solution to the same error message. Hopefully this will help someone else.

I was able to solve it by making sure my collection was statically defined (field names and data types provided) as opposed to a dynamic collection that is defined during runtime based on what is passed to it. When concatenating one or more fields from a dynamic collection in an expression, you may encounter this error message. But, if you change to a statically defined collection, then the error will not occur when validating the expression since the field(s) and respective data type(s) from the collection used within the concatenation expression are "known".
 
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