I can't figure out what this error message means. It occurs on certain items only. I don't know what column value is null from the error message.

Details: An unhandled exception occurred during the execution of the workflow instance. Exception details: System.ArgumentNullException: Value cannot be null. Parameter name: String at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) at Microsoft.Activities.Expressions.ParseNumber1.Execute(CodeActivityContext context) at System.Activities.CodeActivity1.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager) at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation) Exception from activity ParseNumber ToString DynamicActivity Else If Then If Sequence 7 Then If Then If Current Dates Sequence Flowchart Sequence UpdateIOB.


1 Answer 1


It means the workflow couldn't find a specific parameter (called String, not a useful parameter name) when it was trying to convert it from a String to a Number (Parameter name: String at System.Number.StringToNumber).

It looks like it's happening with the activity ParseNumber ToString DynamicActivity before going into more conditional statements leading to something called UpdateIOB.

Check your workflow for any conversions to numbers and figure out what items aren't supplying it a value (it's either blank or doesn't exist so it can't reference it).

  • 1
    After displaying all columns in a datasheet view, I found the field that has a null value. The workflow basically updates another list (In Out Board or IOB) but it requires to know the associated ID number. For some reason, several items from the source list (Absence Request) was not populating the IOBID field. After I manually updated the IOBID field, resumed the workflow, the error message went away. I still need to figure out why it wasn't populating the IOBID field...but that's another issue. Aug 28, 2017 at 19:50

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