You have made changes to your backend reporting database, rerun your Report Preview but the values havn’t changed ! One of best recommendations I can make to SQL 2012 Reporting Services developers is to disable preview caching on the development machine. Of course you won’t want to change this in production, however in your dev environment, this will save you from the confusion and additional time spent forcing a refresh on reports.
To disable the Reporting Services Designer Preview cache go to C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\PrivateAssemblies and open the RSReportDesigner.Config file for edit. Now locate the CacheDataForPreview tag and change the value to False. Save the file.
For SQL Server 2008 Business Intelligence Studio users, you will find the file in the C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\PrivateAssemblies path.