I am getting the below error for my custom reports while i am trying to add a calculation with in the visual studio. Please give me the solution for it. failed to load host assembly details could not load file or assembly 'Microsoft.reportingservices.processingCore, version 10.0.0, culture=neutral,publickeytoken=89845cd8080cc91' or one of its dependencies.The parameter is incorrect, culture=neutral,publickeytoken=89845cd8080cc91' or one of its dependencies.The parameter is incorrect

Hi Sudhakar.mandava, The error message indicates that the issue occurs when an expression loading the Microsoft.reportingservices.processingCore.dll assembly. To resolve the issue, I suggest that you try the following suggestions: Suggestion 1: Clear the C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files folder. If it is a 64-Bit Operating System, please use Framework64 to replace Framework in the above path. Clearing this folder won't cause any negative affect. Suggestion 2: Navigate to the C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\PrivateAssemblies folder. Check whether there are custom entries in the "RSReportDesigner.config" and the "RSPreviewPolicy.config" files and remove anything that is not necessary for this report to run. To do this, we can compare the config files with a SSRS installation where this custom assembly was not deployed. Suggestion 3: Locate the target CodeGroup entry in the RSPreviewPolicy.config, set the "PermissionSetName" value to "FullTrust". For the step by step guidelines about using custom assembly in a SSRS report, you can refer to the following blog: http://www.devx.com/codemag/Article/33656 Hope this helps. Regards,Mike Yin TechNet Community Support

Thanks for the solution, i will try this and let you know. Thanks, Sudhakar.