Report Designer Preview is not working when using ObjectDataSource

AUTHOR: Petar R

DATE POSTED: March 06, 2014

Generally Visual Studio Report Designer operates inside the Visual Studio application. Thus when previewing a report the report constructor is executed in the context of the Visual Studio application and all the configuration settings are obtained from the Visual Studio's devenv.exe.config file. If not taken upon consideration, this might lead to two major issues - ConnectionStrings and AssemblyReferences mismatch.

• Connection Strings

  As described in MSDN, the ConfigurationManager.ConnectionStrings property gets the ConnectionStringsSection data for the current application's default configuration. Generally in case of Visual Studio this is devenv.exe.config. The SqlDataSource component is particularly designed to use the current's project configuration file. However if your custom data access layer (DAL) is reading the ConfigurationManager.ConnectionStrings from the report that is previewed you get all connection strings defined in the devenv.exe.config file. In order to avoid the error you have several options:
  
  1. Hard code the ConnectionString in you DAL;
  2. Use an actual application to view your reports in runtime instead of the Previews;
  3. Add the required ConnectionString in devenv.exe.config;
  4. Use the SqlDataSource instead that will resolve the ConnectionStrings in the reports projects.

• Assembly References

  The AssemblyReferences section contains assembly descriptions that are used to resolve the necessary assemblies during design and/or processing stage. When designing a report that uses ObjectDataSource in Visual Studio Designer, the engine will add the necessary AssemblyReferences entries in the configuration file of the current project. However, when you preview the report in a standalone application, you need to add these entries in the application configuration file so the processing engine would be able to resolve the necessary types.

Generally to debug your data access layer while you are using the Visual Studio Report Designer you have to open another Visual Studio instance, select Debug->Attach to process to debug another instance of devenv.exe and select Debug->Exception... to enable  the First Chance Exceptions.