I was working on some enhancements on an existing SQL Server Reporting Services (SSRS) report & so before started adding enhancements to the report, I made a copy of the existing report. And after that, I tried running the report as-is to make sure everything was functioning as it should. But I got an error:
If you look at the expression which is throwing the error, you’ll see something like code.<custom function> in the expression.
To solve the error, you’ll have to define the custom function for your report. In my case, I had to copy the code from the existing report to the new version of report that I was working on.
To do that, follow the steps:
Design View > Right click on the surface outside the border of the report > Report Properties > Code:
I hope this helps if you run into this SSRS error.