Make sure you’ve assigned the values for TransactionData.
TransactionData.Select(“type=‘WI5’ and Status=‘Open’”)
Check the count of Transaction Data, if zero, don’t proceed further. else it will work.
In a IF check this condition and place your assign in the true part.
TransactionData IsNot Nothing AndAlso TransactionData.Rows.Count >1
if condition like this which i was check
Usually this error occurs when the associated activity has a variable with null values in it
So here TransactionData has no value in it
Kindly check once with source of this variable like from where it is getting value, and is it assigned properly or not
If it’s from arguments kindly check whether it is assigned correctly in INVOKE WORKFLOW FILE activity