Debugging #Error in SSRS report caused by attempts to convert non-numeric strings

While testing another modified SSRS report I noticed that certain values were not shown, only the message:

#Error

 

Checked the ReportServerService__*.log and ExecutionLog* database views, but they contained no clues about the error.

 

Then I used procdump to log exception messages from ReportingServicesService.exe with:

procdump.exe -f "" -l -e 1 ReportingServicesService.exe

 

Part of the result was:

[13:15:59] Exception: E0434F4D.System.FormatException ("Input string was not in a correct format.")
[13:15:59] Exception: E0434F4D.System.FormatException ("Input string was not in a correct format.")
[13:15:59] Exception: E0434F4D.System.InvalidCastException ("Conversion from string " norm" to type 'Decimal' is not valid.")

 

I extracted and ran the dataset query in SQL Server Management Studio.

Then looked for “norm” strings and found them in a column normally used to store numbers.

Attempts to convert these caused the problem.

 

My solution was to exclude them from the dataset query by adding:

AND ISNUMERIC(ValueString) = 1