Stumbled on an obscure problem. Posting this because my searches of stack overflow did not find my answer. Hopefully this will help someone else.
Problem: My reporting services report will compile, but at run-time provides an error along the lines of:
[BC30456] 'RdlObjectModel' is not a member of 'Reporting Services'
This happened after I copy/pasted an entire tablix over from one report to another.
After I reversed the change and removed the tablix, it worked again.
The original report with the tablix I'm copy/pasting works fine.
Found this bug report which exactly explains the problem I had:
Summary of the above: When you copy/paste reporting services expressions from one place to another (I copied an entire tablix, with expressions in it) all the pieces of that expression get expanded to their full names. There is a bug specific to when you copy/paste an expression containing "Cstr()". It gets a full name that does not resolve correctly.
Fortunately this is easy to fix, even if you have a ton of such expressions in your report. --Go to View > Code Do a find for "RdlObjectModel" or "Cstr". You are looking for something like this:
Microsoft.ReportingServices.RdlObjectModel.ExpressionParser.VBFunctions.Cstr([your expression here])
-Remove everything from "Microsoft" to "Cstr" so it looks like this:
Cstr([your expression here])
-Save. You have essentially undone what Reporting services so "helpfully" tried to do when you copied/pasted the expresion in the first place.