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Troubleshooting Custom Extension Loading Errors in SQL Server Data Tools

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Developing and deploying custom extensions is a powerful way to extend the capabilities of SQL Server Reporting Services (SSRS). These extensions can provide functionality not available out-of-the-box, such as connecting to unique data sources through custom data processing extensions. However, integrating these custom components into the development environment, specifically SQL Server Data Tools (SSDT), can sometimes lead to unexpected errors, preventing developers from utilizing their extensions effectively within the report design process. This article focuses on a specific issue encountered when loading custom data processing extensions in SSDT for SQL Server 2012, providing a detailed explanation of the problem and a step-by-step resolution.

This troubleshooting guide is applicable to various editions of SQL Server 2012 where SSDT is used for developing Reporting Services projects.

Applies to: SQL Server 2012 Enterprise, SQL Server 2012 Business Intelligence, SQL Server 2012 Developer, SQL Server 2012 Standard, SQL Server 2012 Web.

Symptoms

Consider a common development scenario involving custom Reporting Services components. You have developed a custom data processing extension designed to retrieve data for your reports from a specialized system or API. This extension is built upon and references the Microsoft.ReportingServices.Interfaces.dll assembly, a core component providing the necessary interfaces for extending SSRS functionality. Critically, the version of this assembly referenced by your custom extension might be one that shipped with earlier versions of Microsoft SQL Server Reporting Services, such as SQL Server 2005, SQL Server 2008, or SQL Server 2008 R2.

Following the development and compilation of your custom extension, you install SQL Server Data Tools (SSDT), which is the primary integrated development environment (IDE) for Business Intelligence projects in SQL Server 2012, based on the Visual Studio 2010 shell. You then proceed to deploy your custom data processing extension assembly to the appropriate location where SSDT can discover and load it. This deployment might involve placing the assembly in the PrivateAssemblies folder of the Visual Studio/SSDT installation directory or installing it into the Global Assembly Cache (GAC), depending on the specific configuration and security requirements.

Now, attempting to use this custom extension within SSDT leads to a problem. When you create a new Report Server Project based on the Business Intelligence project templates and subsequently try to add a new data source to a report, intending to select your custom data processing extension from the list of available data source types, the process fails. Instead of seeing your extension listed or being able to configure it, you are presented with an error message.

The error message indicates that the selected data extension is either not installed correctly or cannot be loaded by the environment. A typical error message you might encounter during this process is:

Unable to connect to data source '<Data Source Name>'. The selected data extension '<Custom Extension Name>' is not installed or cannot be loaded. Verify that the selected data extension is installed on the client for local reports and on the report server for published reports.

This error message is frustrating because you know the extension assembly is present, yet the development environment cannot seem to recognize or load it correctly, preventing you from designing reports that rely on this custom data source.

Troubleshooting SQL Server Data Tools Loading Errors

Understanding SSRS Extensibility

SQL Server Reporting Services was designed with extensibility in mind, allowing developers to integrate custom logic at various points in the reporting lifecycle. This is achieved through different types of extensions: data processing extensions (for connecting to data sources), delivery extensions (for distributing reports), rendering extensions (for outputting reports in different formats), security extensions (for custom authentication/authorization), and report definition custom items (for adding custom visualizations). The focus of this issue is on data processing extensions, which require SSRS (and by extension, SSDT’s report designer) to load an assembly that implements specific interfaces defined in Microsoft.ReportingServices.Interfaces.dll.

Creating a custom data processing extension involves developing a .NET assembly that implements the IDataProcessingExtension interface (or related interfaces) found in the Microsoft.ReportingServices.Interfaces.dll. The assembly must be strong-named and deployed to a location where the SSRS runtime (or SSDT’s design/preview environment) can find and load it. Configuration files (rsreportserver.config on the server, and configuration files for the IDE/previewer on the client) are then updated to register the extension with a unique name.

The Role of SSDT and Visual Studio

SQL Server Data Tools (SSDT) in the context of SQL Server 2012 was essentially a specialized shell built upon Microsoft Visual Studio 2010. When you install SSDT, it provides project templates and tools specifically for developing SQL Server databases, Integration Services packages, Analysis Services cubes, and Reporting Services reports. For Reporting Services projects, SSDT includes a report designer environment that mimics the SSRS runtime behavior to allow local previewing and testing of reports. This environment needs to load any custom extensions, including data processing extensions, that the reports might use.

The report designer and the local previewing service within SSDT rely on configuration files, similar to how the SSRS Report Server does, to understand which extensions are available and how to load them. These configuration files dictate assembly loading behavior, including how the runtime resolves references to dependent assemblies, particularly those that might exist in multiple versions. This is where assembly binding redirection becomes relevant.

Deep Dive: Assembly Loading and Binding Redirection

In the .NET Framework, assemblies are the fundamental unit of deployment, versioning, and security. When one assembly (like your custom extension) references another assembly (like Microsoft.ReportingServices.Interfaces.dll), the .NET runtime needs to locate and load the referenced assembly. This process involves checking the application’s base directory, searching configured private assembly paths, and looking in the Global Assembly Cache (GAC).

Assembly binding redirection is a mechanism that allows applications to specify that when the runtime attempts to load a particular version of an assembly, it should instead load a different version of that same assembly. This is crucial for resolving version conflicts, allowing applications built against older versions of libraries to run with newer versions without recompilation. Binding redirection is typically configured in the application’s configuration file (e.g., app.config, web.config, or in the case of SSDT, devenv.exe.config and PreviewProcessingService.exe.config). The configuration uses the <dependentAssembly> and <bindingRedirect> elements within the <assemblyBinding> section.

A <bindingRedirect> entry specifies an oldVersion range and a newVersion. When the runtime encounters a reference to an assembly within the oldVersion range, it redirects the request to load the assembly specified by newVersion. This mechanism relies on the assemblies having the same strong name (specifically, the same publicKeyToken).

<dependentAssembly>
    <assemblyIdentity name="AssemblyName" publicKeyToken="ThePublicKeyToken" culture="neutral"/>
    <bindingRedirect oldVersion="VersionRange" newVersion="SpecificVersion"/>
</dependentAssembly>

Understanding this concept is key to diagnosing the issue described, as the problem stems from an incorrect binding redirection configuration installed by SSDT.

The Cause

The root cause of the loading error lies within the configuration files used by SQL Server Data Tools for its operation and local report previewing. During the installation of SSDT for SQL Server 2012, a bug in the setup process introduces incorrect or incomplete assembly binding redirection entries into two crucial configuration files: devenv.exe.config and PreviewProcessingService.exe.config.

The devenv.exe.config file is the main configuration file for the Visual Studio 2010 shell that hosts SSDT. The PreviewProcessingService.exe.config file is used by the separate process responsible for rendering and previewing reports locally within the SSDT environment. Both files are critical for ensuring that the SSDT environment can correctly load all necessary assemblies, including custom extensions and their dependencies.

The incorrect entry added by the setup specifically affects the loading of the Microsoft.ReportingServices.Interfaces.dll assembly. The problematic entry resembles the following:

<dependentAssembly>
    <assemblyIdentity name="Microsoft.ReportingServices.Interfaces" publicKeyToken="89845dcd8080cc91" culture="neutral"/>
    <bindingRedirect oldVersion="9.0.242.0" newVersion="10.0.0.0"/>
</dependentAssembly>

This configuration tells the .NET runtime that whenever an assembly requests version 9.0.242.0 of Microsoft.ReportingServices.Interfaces.dll (which is the version commonly referenced by extensions built against SQL Server 2005, 2008, or 2008 R2 interfaces), the runtime should instead attempt to load version 10.0.0.0.

The issue arises because version 10.0.0.0 of Microsoft.ReportingServices.Interfaces.dll might not be present on the system where SSDT 2012 is installed, especially if only SQL Server 2012 components are installed. SQL Server 2012’s Reporting Services components, including the interface assembly, typically ship with version 11.0.0.0. Therefore, when your custom extension, built against version 9.0.242.0, is loaded by SSDT, the binding redirection erroneously points to a non-existent assembly version (10.0.0.0) instead of correctly redirecting to the available version (11.0.0.0). This failure to load the dependent interface assembly prevents the custom extension itself from being loaded successfully by the SSDT environment, leading to the error message you see.

Resolution

The resolution to this issue involves correcting the assembly binding redirection entries in both the devenv.exe.config and PreviewProcessingService.exe.config files. By providing the correct redirects, you ensure that SSDT’s environment can properly load custom extensions that were built against older versions of the Microsoft.ReportingServices.Interfaces.dll assembly by directing the runtime to the version available with SQL Server 2012 (version 11.0.0.0).

To resolve the problem, follow these steps carefully:

  1. Locate the Configuration Files: The configuration files are located within the installation directory of Microsoft Visual Studio 2010, which hosts SSDT 2012.

    • The devenv.exe.config file is typically found in the IDE subdirectory of the Visual Studio 10.0 installation path. The default location is usually:
      %ProgramFiles(x86)%\Microsoft Visual Studio 10.0\Common7\IDE (on 64-bit systems) or %ProgramFiles%\Microsoft Visual Studio 10.0\Common7\IDE (on 32-bit systems).
    • The PreviewProcessingService.exe.config file is located within the PrivateAssemblies subdirectory under the IDE path. The default location is usually:
      %ProgramFiles(x86)%\Microsoft Visual Studio 10.0\Common7\IDE\PrivateAssemblies (on 64-bit systems) or %ProgramFiles%\Microsoft Visual Studio 10.0\Common7\IDE\PrivateAssemblies (on 32-bit systems).

    You will need administrative privileges to modify these files. It is strongly recommended to create a backup copy of each file before making any changes.

  2. Edit devenv.exe.config: Open the devenv.exe.config file in a text editor (like Notepad or Visual Studio itself, run as administrator).

  3. Locate the Incorrect Entry: Search for the <dependentAssembly> section related to Microsoft.ReportingServices.Interfaces. You should find the problematic entry mentioned in the cause:

    <dependentAssembly>
    <assemblyIdentity name="Microsoft.ReportingServices.Interfaces" publicKeyToken="89845dcd8080cc91" culture="neutral"/>
    <bindingRedirect oldVersion="9.0.242.0" newVersion="10.0.0.0"/>
</dependentAssembly>

  4. Replace with Correct Entries: Delete or comment out the incorrect <bindingRedirect> line. Replace the entire <dependentAssembly> block for Microsoft.ReportingServices.Interfaces with the following corrected configuration. This configuration includes binding redirects for multiple older versions, ensuring compatibility with extensions built against SQL Server 2005 (8.0.242.0), SQL Server 2008/R2 (9.0.242.0), and potentially an intermediate version (10.0.0.0), redirecting all of them to the SQL Server 2012 version (11.0.0.0).

    <dependentAssembly>
    <assemblyIdentity name="Microsoft.ReportingServices.Interfaces" publicKeyToken="89845dcd8080cc91" culture="neutral" />
    <bindingRedirect oldVersion="8.0.242.0" newVersion="11.0.0.0" />
    <bindingRedirect oldVersion="9.0.242.0" newVersion="11.0.0.0" />
    <bindingRedirect oldVersion="10.0.0.0" newVersion="11.0.0.0" />
</dependentAssembly>

    Note: The first <assemblyIdentity> line inside the <dependentAssembly> block is often redundant or malformed in the original problematic file; including a single, clean <assemblyIdentity> line followed by the <bindingRedirect> lines is the standard correct format. The provided corrected block ensures this standard structure.

  5. Save devenv.exe.config: Save the changes made to the devenv.exe.config file.

  6. Edit PreviewProcessingService.exe.config: Open the PreviewProcessingService.exe.config file in a text editor (run as administrator).

  7. Locate and Replace in PreviewProcessingService.exe.config: Repeat steps 3 and 4 for the PreviewProcessingService.exe.config file. Find the incorrect dependentAssembly entry for Microsoft.ReportingServices.Interfaces and replace it with the same corrected block used for devenv.exe.config.

  8. Save PreviewProcessingService.exe.config: Save the changes made to the PreviewProcessingService.exe.config file.

  9. Restart SSDT: Close all instances of Visual Studio/SSDT that are currently running. Reopen SQL Server Data Tools. The changes to the configuration files will be loaded upon startup.

After performing these steps and restarting SSDT, you should now be able to create a new data source in your Report Server Project and select your custom data processing extension without encountering the loading error. The corrected binding redirects allow the SSDT environment to successfully load your extension, as it can now correctly resolve its dependency on Microsoft.ReportingServices.Interfaces.dll to the version available in the SQL Server 2012 installation.

Version Compatibility Overview

Understanding the relationship between SQL Server/SSRS versions and the corresponding versions of the core Microsoft.ReportingServices.Interfaces.dll assembly is helpful in diagnosing compatibility issues. While extensions are often forward-compatible to some degree (especially with correct binding redirects), major version changes can sometimes introduce breaking changes.

SQL Server/SSRS Version Microsoft.ReportingServices.Interfaces.dll Assembly Version (Typical) Notes
SQL Server 2005 8.0.242.0 Original version referenced by extensions
SQL Server 2008 / 2008 R2 9.0.242.0 Later version referenced by extensions
SQL Server 2012 11.0.0.0 Version shipped with SSRS 2012
SQL Server 2014 12.0.0.0 Version shipped with SSRS 2014
SQL Server 2016 / 2017 13.0.0.0 / 14.0.0.0 Versions shipped with later SSRS versions

The corrected binding redirects in the resolution essentially map requests for versions 8.x, 9.x, and 10.x to version 11.x, ensuring extensions built against earlier interfaces work in the SQL Server 2012 SSDT environment.

Deployment Considerations

While this article primarily addresses a client-side development environment issue within SSDT, it’s important to remember that custom extensions also need to be correctly deployed to the SSRS report server environment if reports using them are to be published and run server-side. Server-side deployment involves placing the extension assembly in the server’s ReportServer\Bin directory and registering it in the rsreportserver.config file. Similar assembly binding redirection issues can occur on the server if the rsreportserver.config file or the server’s machine configuration files are not correctly configured, especially when running reports developed in a newer SSDT against an older report server, or vice-versa, although the specific configuration needed may differ slightly.

Additional Troubleshooting Tips

If the resolution steps above do not immediately fix the issue, consider the following:

  • Verify Assembly Deployment: Double-check that your custom extension assembly (.dll file) is correctly placed in the PrivateAssemblies folder of the Visual Studio 10.0 IDE directory (%ProgramFiles(x86)%\Microsoft Visual Studio 10.0\Common7\IDE\PrivateAssemblies). This is the standard location for SSDT to find design-time extensions.
  • Check RSReportDesigner.config: While devenv.exe.config and PreviewProcessingService.exe.config handle assembly loading for the IDE and previewer, the RSReportDesigner.config file (located in %ProgramFiles(x86)%\Microsoft Visual Studio 10.0\Common7\IDE\PrivateAssemblies) is where the extension is registered for the designer to list it as an option. Ensure your extension is correctly registered here under the <Data> <DataSources> section.
  • Global Assembly Cache (GAC): If your extension assembly is installed in the GAC, ensure it was installed correctly for the target .NET Framework version used by SSDT (likely .NET Framework 4).
  • Dependencies: Verify that your custom extension assembly has no other missing dependencies. Use tools like Assembly Binding Log Viewer (Fuslogvw.exe) to diagnose .NET assembly loading failures. This tool can provide detailed logs about why an assembly load request failed, including which path was searched and why a binding redirect might have failed.
  • SSDT Installation Integrity: In rare cases, the SSDT installation itself might be corrupted. Consider running a repair of the SQL Server Data Tools installation.

Conclusion

Encountering errors when loading custom extensions in development tools like SQL Server Data Tools can be a hurdle, but often the cause is related to environment configuration rather than the extension code itself. As demonstrated by the specific issue in SQL Server 2012 SSDT, incorrect assembly binding redirection is a prime example of such a configuration problem. By understanding how .NET assembly loading works and how configuration files like devenv.exe.config and PreviewProcessingService.exe.config influence this process, you can effectively diagnose and resolve these issues. Applying the corrected binding redirects detailed in this article should restore the functionality of loading your custom data processing extensions within the SSDT 2012 environment, allowing you to proceed with your report development.

Have you encountered this specific error or similar issues when working with custom SSRS extensions in SSDT? Do you have other troubleshooting tips or experiences to share? Join the discussion below and let us know!

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