Note: This issue should be resolved by converting VS 2008 (SSRS 2005) RDLCs to VS 2010 (SSRS 2008) RDLCs and adding Microsoft.ReportViewer.WebForms.dll Version 10 reference to your .NET Framework 3.5 project’s references instead of Version 9
Thanks to the Framework Multi-Targeting new feature of Visual Studio 2010 which enables .NET developers to develop .NET applications which target the previous versions of .NET Framework using Visual Studio 2010.
Based on this, I have decided to remove all previous Visual Studio versions and install Visual Studio 2010.
By the way, I have struggled to uninstall Visual Studio 2008. When I used the regular uninstall through Windows Control Panel. I have got a message which says something like “Can’t uninstall Visual Studio 2008”.
After few trials to find what is the wrong with my system, I did a quick search I found that this problem raised due to some Visual Studio 2008 hot fixes and updates which cannot be removed by the normal uninstall process. Therefore Microsoft provides Auto Uninstall Tool to completely remove Visual Studio 2008.
If you run this tool, the below screen will be displayed. just click Yes to start the cleaning process.
Let’s get back to the main reason I did this blog post for. I used Visual Studio 2010 to open ASP.NET application developed using .NET Framework 3.5. I got the below message when I tried to open RDLC report.
This message asks if I want to convert RDLC report format to 2008. After I canceled the conversion, the report designer showed “The version of the report definition language (RDL) is not support by Visual Studio 2010 Report Designer” message as you can see at the following figure
This problem happens due to Visual Studio 2008 Report Designer uses SQL Server Reporting Service (SSRS) 2005 format to work with RDLC reports and Visual Studio 2010 uses SSRS 2008 format.
It supposed that Report Designer 2010 has the ability to open and edit the previous RDLC formats for the sake of back compatibility.
I recalled that after SSRS 2008 was released, developers were not able to create RDLC reports in 2008 format and the reason of that is Visual Studio 2008 released before SQL Server 2008!.
However, I still have the ability to convert the report to RDLC 2008 format which is weird. .NET Framework 3.5 “Microsoft Report Viewer” control doesn’t support RDLC 2008 format in Local mode.
The following figure shows the message you’ll get if you try to run RDLC 2008 report under .NET Framework 3.5.
The question here is: Why I can convert RDLC 2005 to RDLC 2008 whereas I still use .NET Framework 3.5?!
Ahmed Elbaz's Blog 
Did you check this?
http://forums.asp.net/t/1433651.aspx#3239113
It’s not the same but suggests if you don’t have the SQL Server version (not just client tools) on the developer machine it may be the problem, which may apply to SQL Server 2005 also.
As mentioned in this link, Local mode is a different story.When using local mode with the VS 2005 or VS 2008 viewer controls, you are using the same report processing engine that was shipped with SQL Server 2005. This engine does not understand the new report definition schema.
Anyway, I can not edit RDLC 2005 format reports using Visual Studio 2010 Report Designer.
I’m having the same problem. I can open the RDLC in VS2008 but not in VS2010 and there’s no clear way to do the conversion. This appears to have nothing to do with what version of SQL server is installed locally.
Any help is appreciated.
Yes Marx nothing to do with your local machine. VS2008 RLDC report designer uses the same engine used in SSRS 2005 and VS2010 report designer uses SSRS 2008 engine, so we cannot develop RDLC 2005 format using VS2010 report designer especially when we develop reports in Local Mode
Not sure what you mean by Local mode, I don’t think you can use VS2010 for RDLCs that were produced in VS2008 no matter what.
Very aggravating.
Yes, we cannot use VS2010 for updating VS2008 RDLCs
Use the ReportViewer 10.0 control that was just released and everything will work. Thanks.
Hi, I had the same issue.
You just need to remove your old reference Microsoft.ReportViewer.WebForms.dll (Version 9) and replace it by the new one (version 10). Finally, change the register tag in your aspx page to reference the new version
Everything should work !
Yes, It works. thanks
Thanks for your reply. It Works!!!
I downloaded and installed the Report Viewer WebForm.DLL, so that a SSRS 2005 rdlc file now can be working inside VS2010 IDE. However, when such report is moved to run from IIS server, then it no longer works. In particular, this report is supposed to display a PDF report, but when it is running off a server, it only display garbage dump. Any help is highly appreciated. Thank you.
OK. I modified the web.config so all the report viewer and rdlc assemblies are pointing to the V10.0.0.0. Now it prints OK. The only pending issue is the VS2010 Project “Publish” feature will send the rdlc file straight to the bin folder at the target IIS server. The IIS serve we have is still IIS 6.0 So if anyone can provide a solution, will be greatly appreciated.
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Discovered this on Google and I am happy I did
Does anyone came up with how to make SSRS 2005 reports to be migrated to VS 2010 .Thanks for your help in advance.