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Posted 11 Nov 2012


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Zip Rendering Extension for SQL Server Reporting Services 2005/2008/2012

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14 Aug 2013CPOL13 min read
How to create and deploy a SSRS rendering extension, explained by a functional Zip Rendering extension for SSRS 2005, 2008 (R2) and 2012.


In Reporting Services’ Report Manager you can export reports as Excel, CSV, PDF, and other formats. But what if you want to add a watermark to every PDF? Or, change an exported Excel's sheet names from 'Sheet2' to something meaningful? Or do any kind of processing for that matter on an existing (built-in) Rendering Extension?

This article shows how to make an SQL Server Reporting Services (SSRS) Rendering Extension that can change the output of other renderers before it is sent to the client - in this case, it compresses one or more reports in a .zip file.  

There's also a general explanation of deployment and troubleshooting that is useful for any Rendering Extension. I have tried to make things as clear and complete as possible. Some documentation on deployment is out there but spread out all over the place (particularly on MSDN). This article should help anyone get started with Rendering Extensions.  

Table of Contents:

List of MSDN links:


In one of my projects I created a report that contained tens of megabytes of data. This report was later scheduled to be sent daily via e-mail. That is of course way too large to e-mail, but if you want to send data to customers you often have no choice.

So I started looking for a smaller alternative. The smallest existing export available is .CSV, however you can only export data structured as tables in a .CSV file. Also dealing with .CSVs is just not practical except when you set up automated data transfer.

Then I read this excellent article about rendering extensions by one of my fellow countrymen: This article details the modification of an exported pdf (watermark).

So I thought, if you can change a pdf, surely you can also zip the output and return a zip file? The basic idea of this ZipRenderer is the same: Get a reference to an existing renderer, make it render a report. Get the output and do something with it.

Although the article on is a great start (and I recommend you read it, too) there were still a lot of things to find out. For example, the PdfRenderer that was available in 2005, isn't anymore from 2008 onward, so the method from the article doesn't work anymore.

Using the code

This part is about deployment; the steps below apply to any rendering extension. (except those that are obviously related to the ZipRenderer) 

Build and deploy the extension 

Open the appropriate project for your environment. The 2012 project is usable for both SSRS 2008 and 2012. Because this is a normal .NET assembly project, BIDS is not necessary.   

  1. Add references to:


    the SSRS 2005 project also needs

    all of these are in [SQL Reporting Services folder]\ReportServer\Bin\ on the SQL Server machine. I found it easiest to copy the entire contents of that bin folder to the development machine for investigation and future use in extensions.

    The ExcelRendering and ProcessingCore will give a warning about a newer .NET version, you can safely ignore this. (see

  2. For the zip functionality we need the DotNetZip library: Download the latest Runtime, extract Ionic.Zip.dll from one of the bin/Release folders (zip-v#.# contains the normal Zip compression) and add a reference to Ionic.Zip.dll.
  3. Build the project.
  4. Move ZipRenderer.dll and Ionic.Zip.dll from the output folder to [SQL Reporting Services folder]\ReportServer\Bin\.
  5. You may notice there are a -lot- of other dlls in the output folder. These are all reportserver related and do not need to be copied to the reportserver. (In fact, they originated there).

Server Configuration 

Now there is some configuring to do to make our extension show up in the report manager. Thanks to this article that isn’t too hard.

  1. Add this to [SQL Reporting Services folder]\ReportServer\rsreportserver.config directly above the </Render> tag:
    <Extension Name="ZIPEXCEL" Type="ZipRenderer.ZipRenderingProvider,ZipRenderer">
                <ZipRenderer description ="Zipped Excel">
                        <SubRenderer extension="xls" format="EXCEL" />

    (Note the custom tags inside DeviceInfo.)

  2. And add this to [SQL Reporting Services folder]\ReportServer\rssrvpolicy.config: 
  3. XML
        Name="Zip Renderer"
        Description="This code group grants Zip Renderer code full trust.">
       Url="[SQL Reporting Services folder]\ReportServer\bin\ZipRenderer.dll" />

    Place this XML in the config file as explained on MSDN:

    For extensions and custom assemblies that you develop, it is recommended that you place your custom code groups directly below the existing entry for the URL membership "$CodeGen$/*"

    This is an UrlMembershipCondition that uses a path, or URL, to the DLL. Remember to change the above Url to the correct path to ZipRenderer.dll!

    You can also use a StrongNameMembershipCondition, see Broes’ article part 2 again. It takes some more actions to set up. Take a look there if you want to deploy your assembly in that way. 

  4. Finally, restart Reporting Services service to apply the changes to the .config files.

    *newer versions of SSRS detect changes to the config files and automatically restart / reconfigure the service. This is visible in the Application Event log as an Information event like "The RSReportServer.config file has been modified". 


Now if everything is set up OK, you should see the extension show up as "Zipped excel" in the export drop down menu when you run a report. If that is the case, congratulations, you have just deployed the extension. Click the export link and you will download a zip file containing a .xls. 

Now, a lot of things could have gone wrong - I think I have seen them all - here are some tips if it doesn't show up or work:

  • If the extension does not show up at all, most likely the configuration files were not changed correctly (wrong path to ZipRenderer.dll), the files were not saved to disk or not applied. Make sure they are saved, then restart SQL Server reporting services. In SSRS 2005 it might also help to restart the entire website from IIS.
  • Also check the Application Event log for error messages such as "Report Server (MS SQL Server) cannot load the ZIPEXCEL extension." which will point you in the right direction. There may be useful information in the stack trace of ASP.NET Warning events nearby the Error event.
  • Check the latest log files folder in [Reporting Services Folder]\LogFiles. Sort by date modified and open the latest log files. Then scroll down and look for a stack trace.
  • If you get a Server error page when selecting ZipExcel, you can also find details in the page itself. Open the report page on the server to see the error details if they aren't shown.  


If you have Visual Studio running on your SSRS machine, debugging is easy, however this is not documented on MSDN. (The page Debugging Delivery Extensions comes closest)   

First, copy the ZipRenderer.pdb file to the server. Otherwise the debugger will complain that Symbols are not loaded. To start debugging:  

  • Run Visual Studio as Administrator and open the project  
  • Select Tools - Attach to Process.
  • Check "Show processes from all users" and "Show process from all sessions" if necessary 
  • Find and select the executable that is hosting the ZipRenderer DLL  
    • SSRS 2008+: ReportServicesService.exe
    • IIS6: w3wp.exe
    • IIS7: aspnet_wp.exe
  • Attach.

Image 1

If you cannot run Visual Studio on the server, you can use Remote Debugging. How to set it up is explained here on MSDN: Remote Debugging  Setup. How much work this is depends on your server configuration. I'll leave that for other dedicated articles to explain. 

Points of Interest 

Now.. finally it is time for all the nifty bits of code in the project. The actual zipping process in the code is quite small - it is getting to the renderers and the right datastreams that's a challenge.

The built-in ExcelRenderer

Problem 1: read the output of the built-in ExcelRenderer 

One of my main concerns at first was how to get to the output from other built-in renderers, especially the ExcelRenderer. In SSRS 2005, 2008 and 2012 the Excel renderer is public in the Microsoft.ReportingServices.ExcelRendering namespace.

So far so good, you can add ExcelRenderer to your references, instantiate it and make it render some reports. However: ExcelRenderer does not behave nicely; it closes the MemoryStream you give it from the CreateAndRegisterStream callback. There's no way to get the results. Even ToArray() on the MemoryStream does not work: only part of the excel file is returned and the rest chopped off so you end up with a corrupt file if you try to write it.

I’m no Stream expert but I think it’s behaving this way because the Excelrenderer calls the CreateAndRegisterStream multiple times; once for every sheet or embedded image.

Solution: the UnclosableMemoryStream

After a lot of hair-pulling I decided to just subclass MemoryStream to stop the ExcelRenderer from closing my MemoryStreams. A simple solution, but it worked quite well!

class UnclosableMemoryStream: MemoryStream
    private bool allowClose; 
    public bool AllowClose
        get { return allowClose; }
        set { allowClose = value; }
    public override void Close()
        if (AllowClose)

This stream will not close until you allow it to.. So with this class in place you can pass instances of it to the ExcelRenderer in the CreateAndRegisterStream callback and still read the contents later.

Problem 2: Multiple streams

With the MemoryStream issue solved, something also needs to be done about the multiple streams the ExcelRenderer needs. 

The renderer's CreateAndRegisterStream is called only once with the StreamOper.CreateAndRegister parameter value. That is the main Stream that contains all of the excel contents in the end so that is the one we will store as RegisteredStream.

Below the Excel version of CreateAndRegisterStream.

(Note: The actual UnclosableMemoryStream instance is created in the wrapper class CreateAndRegisterStreamUnclosableMemoryStream. This class also stores the parameters for the call to CreateAndRegisterStream for later use in the Render method.)

// Intermediate CreateAndRegisterStream method that matches the delegate
// Microsoft.ReportingServices.Interfaces.CreateAndRegisterStream
// It will return a reference to a new MemoryStream, so we can get to
// the results of the intermediate render-step later.
public Stream IntermediateCreateAndRegisterStreamExcel(
    string name,
    string extension,
    Encoding encoding,
    string mimeType,
    bool willSeek,
    StreamOper operation)
    //Create a stream container and store every parameter in it
    CreateAndRegisterStreamStream crss = 
      new CreateAndRegisterStreamUnclosableMemoryStream(
      name, extension, encoding, mimeType, willSeek, operation);
    //Store stream container
    if (operation == StreamOper.CreateAndRegister)
        //Create the main stream. Contents of this stream are returned later
        RegisteredStream = crss.Stream;
    return crss.Stream;

Custom DeviceInfo from the config file

You may have noticed all renderers including the existing ones can be configured from rsreportserver.config. The place to read your own renderer’s configuration and apply it is in IExtension.SetConfiguration

/// <summary>
/// Process XML data stored in the configuration file
/// </summary>
/// <param name="configuration">The XML string from the configuration file that contains extension configuration data.</param>
void IExtension.SetConfiguration(string configuration) 

The parameter "configuration" contains the Inner xml of the <Configuration> tag from rsreportserver.config.

The IRenderingExtension.Render method also has a configuration parameter called deviceInfo, a NameValueCollection. DeviceInfo is also a configuration item from rsreportserver.config, but simplified: It contains every direct child of <DeviceInfo> and its XmlNode.InnerText as the value.

More info on DeviceInfo on MSDN here and here  
UPDATE: Added support for deviceInfo parameters as settings for the zipmodule. See chapter below this one. 

For the zip renderer I have set up a configuration format that allows for multiple SubRenderers - as I call them - to be wrapped in the zip file, AND they can have their own separate DeviceInfo configuration. The contents of each <SubRenderer> are passed through to their respective Renderer objects and used as Configuration string.

An example configuration:

<Extension Name="ZIPEXCELPDF" Type="ZipRenderer.ZipRenderingProvider, ZipRenderer">
      <ZipRenderer description="Zipped Excel + PDF">
          <SubRenderer extension="xls" format="EXCEL" />
          <SubRenderer extension="pdf" format="PDF">

An this is how it’s interpreted:

  • description="Zipped Excel + PDF" is the name you see in Report Manager export list
  • <Subrenderers> tells the extension to use the following SubRenderers:
    • SubRenderer: format EXCEL: Use the ExcelRenderer, use “xls” as the file extension
      • (No additional DeviceInfo)
    • SubRenderer: format PDF: Use the PdfRenderer, use “pdf” as the file extension
      • Add additional DeviceInfo when calling the pdfrenderer: Start at page 3, end rendering at page 4 (Yes, I know, it’s nonsense but just for demonstration)

Code to parse the XML:

/// <summary>
/// Process XML data stored in the configuration file
/// </summary>
/// <param name="configuration">The XML string from the configuration file that contains extension configuration data.</param>
void IExtension.SetConfiguration(string configuration)
    this.configuration = configuration;
    // Create the document and load the Configuration element    
    XmlDocument doc = new XmlDocument();
        //Check for the DeviceInfo element
        if (doc.DocumentElement.Name == "DeviceInfo")
            //Find the ZipRenderer node
            XmlNode zipRendererNode = doc.DocumentElement.SelectSingleNode("ZipRenderer");
            if (zipRendererNode == null)
                throw new System.Configuration.ConfigurationErrorsException(
                    "Missing ZipRenderer node in configuration", doc.DocumentElement);
            //Read this extension's description
            description = zipRendererNode.Attributes["description"].Value;
            //Read all of the SubRenderers configured
            subRenderers = new List<SubRenderer>();
            foreach (XmlNode zippedReportNode in zipRendererNode.SelectNodes("SubRenderers/SubRenderer"))
                    //Try and create a SubRenderer
                catch (System.Configuration.ConfigurationErrorsException ex)
                    //An invalid SubRenderer format was used.
                    throw new System.Configuration.ConfigurationErrorsException(
                        String.Format("The SubReport format {0} could not be found", 
                        ex, zippedReportNode);
                    //Tried this but fails in 2008 / 2012. The ZipRenderer
                    // and the ReportViewer renderer will keep waiting for each other. Deadlock.
                    //TODO: Replace by WebServiceSubRenderer.
                    //subRenderers.Add(new ReportViewerSubRenderer(
                    //        zippedReportNode.Attributes["format"].Value));
    catch (XmlException ex)
        throw new System.Configuration.ConfigurationErrorsException(
                    "Failed to read configuration data: " + ex.Message, ex);

The actual SubRenderer is determined in SubRenderer.CreateSubRenderer(…).

Note that the InnerXml of the SubRenderer nodes is passed through unchanged to the SubRenderer; this may or may not contain extra DeviceInfo. The SubRenderers are responsible for parsing their own configuration string.

Updated: DeviceInfo for the zip process   

Following a reader suggestion the included ziprenderer now also supports the following settings for 

CompressionLevel, CompressionMethodStrategyCommentEnableZip64IgnoreCaseEncryption and Password.
Follow the links for the available values for each configurationitem or have a look at the Ionic.Zip Zip reference
The configuration items do not need to be present however if you enable Encryption, you must also enter a Password value. 

Example configuration:  

<Extension Name="ZIPEXCELOPENXML" Type="ZipRenderer.ZipRenderingProvider,ZipRenderer">
            <ZipRenderer description ="Zipped Excel 2012">
                    <SubRenderer extension="xlsx" format="EXCELOPENXML">

The code that reads the settings ( in ZipRenderingProvider.Render )

//Create a Zip output and tell it to keep the provided stream open - we use it outside the using clause
using (ZipOutputStream zipOutput = new ZipOutputStream(outputMemoryStream, true))
    //Read zip deviceinfo
        if (deviceInfo["CompressionLevel"] != null)
            zipOutput.CompressionLevel = (Ionic.Zlib.CompressionLevel)Enum.Parse(
              typeof(Ionic.Zlib.CompressionLevel), deviceInfo["CompressionLevel"], true);
        if (deviceInfo["CompressionMethod"] != null)
            zipOutput.CompressionMethod = (Ionic.Zip.CompressionMethod)Enum.Parse(
              typeof(Ionic.Zip.CompressionMethod), deviceInfo["CompressionMethod"], true);
        if (deviceInfo["Strategy"] != null)
            zipOutput.Strategy = (Ionic.Zlib.CompressionStrategy)Enum.Parse(
              typeof(Ionic.Zlib.CompressionStrategy), deviceInfo["Strategy"], true);
        if (deviceInfo["Comment"] != null)
            zipOutput.Comment = deviceInfo["Comment"];
        if (deviceInfo["EnableZip64"] != null)
            zipOutput.EnableZip64 = (Ionic.Zip.Zip64Option)Enum.Parse(
              typeof(Ionic.Zip.Zip64Option), deviceInfo["EnableZip64"], true);
        if (deviceInfo["IgnoreCase"] != null)
            zipOutput.IgnoreCase = Boolean.Parse(deviceInfo["IgnoreCase"]);
        if (deviceInfo["Encryption"] != null)
            zipOutput.Encryption = (Ionic.Zip.EncryptionAlgorithm)Enum.Parse(
              typeof(Ionic.Zip.EncryptionAlgorithm), deviceInfo["Encryption"], true);
        if (deviceInfo["Password"] != null)
            zipOutput.Password = deviceInfo["Password"];
    catch (Exception ex)
        throw new System.Configuration.ConfigurationErrorsException(
          "Invalid DeviceInfo configuration value", ex);

    foreach (SubRenderer sr in subRenderers)
    {<span style="font-size: 9pt;">

The built-in PDFRenderer in SSRS 2008 R2 / 2012

In SSRS 2005 you can use the built-in PdfRenderer just like the ExcelRenderer because it is public.

No such luck in SSRS 2008 (R2) / 2012, though. Microsoft has made the PdfRenderer an internal sealed class, so you have to resort to Reflection methods to reach it. Yes, you heard right. Below is the code necessary to do so.

// Initialize the PDF renderer. it is an internal sealed class but we can still get to it using..Reflection! 
if (pdfRendererType == null)
    //1. Load the ImageRendering Assembly
    //Use a disassembler tool like ILSpy to find The AssemblyName, type and constructor
    //methods for other internal renderers in their respective .dlls
    //This is code for the Sql Server 2012 assembly.
    //Replace Version= by Version= and you are good to go for 2008.
    Assembly IR = Assembly.Load(new AssemblyName("Microsoft.ReportingServices.ImageRendering, 
                    Version=, Culture=neutral, PublicKeyToken=89845dcd8080cc91"));
    //2. Read the PdfRenderer type from the Assembly
    pdfRendererType = IR.GetType("Microsoft.ReportingServices.Rendering.ImageRenderer.PDFRenderer");
//3. Create an instance of type PdfRenderer. PdfRenderer inherits from
// IRenderingExtension which is a public interface so cast it to IRenderingExtension
renderer = (IRenderingExtension)pdfRendererType.GetConstructor(BindingFlags.Public | 
             BindingFlags.Instance, null, Type.EmptyTypes, null).Invoke(null);
// /Reflection
// phew..  

The trick to this is that at the end the pdfRenderer is cast to the interface IRenderingExtension. Unless you want to use pdfRender-specific functions, this is where reflection ends. Good thing, too.  

With this code in place the PDF watermark becomes possible in SSRS 2008/2012 !  

A Generic SubRenderer  

For every built-in renderer we need to get a reference to the SSRS renderer class. There are also all kinds of issues with streams to address. You may think: can't you tell the report server to create the report and then get it back? 

Well, we can: with a call to the ReportExecutionService or reportserver URL Access. But, the server has already provided us with our report data: in the report parameter of the IRenderingExtension.Render method. It would be a waste to do nothing with this and rerun the entire report, wouldn't it? 

the ReportViewer to the rescue (or not?)  

You may have noticed in the Report Manager there is no delay if you export a report. This is because it doesn't run the entire report again: it passes the SessionID to the SSRS Engine. This way SSRS knows it needs to reuse the data already shown and just render it differently.  This is also possible in code, see the ReportViewerSubRenderer class (modified code from this blog comment). It generates a HttpWebRequest that looks like this:  


There's a catch. Two actually:

In Subscriptions there is no SessionID available. Without a SessionID the ReportViewerWebControl cannot be used to render a report, it doesn't know which one to render.. 

And, while this worked in SSRS 2005 (from the reportmanager), in SSRS 2008 it seems the engine got smart and blocks additional calls to ReportViewerWebControl; the above request will time out. I assume this is some protection against repeated requests, to safeguard server resources.  

Here's a diagram to illustrate this - remember, this is all founded on observation and may not reflect the actual  process. 

Image 2


Using the webservice / URL access may still be a viable option if you use it together with report data caching. Just set the cache expiration to a small amount like 5 minutes, just enough for the report data to be stored and reused. Just subclass SubRenderer and point to your class in CreateSubRenderer.. - I may add that myself in the future. 

Other than that, the built-in renderers are the most efficient solution. You just need to code every one separately.

Everything would be so much easier if we could just access the <a href="">Report.Render</a>(format, deviceInfo) method like in a Delivery Extension... 


  • Nov 11, 2012 v1.0: Published first article! 
  • Jan 26, 2012 v1.1: Added support for Zip options like CompressionLevel 


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By
Software Developer
Netherlands Netherlands
I am a database-oriented software developer .. or an application-oriented database engineer, depending on the situation.

In past 7 or so years I have created stuff ranging from Windows Services to WPF, from GDI+ to SSIS packages and SSRS extensions.

My goal is to improve life and work for others - which should be the ultimate goal of any good software project.
And my articles on Codeproject can hopefully make you do the same.

Comments and Discussions

QuestionChange excel data before zipping Pin
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QuestionTrying to use IRenderingExtension for formatted text file output Pin
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QuestionAdd Excel document properties Pin
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QuestionHi Pin
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QuestionError while adding zip rendenring option in SSRS 2016. Pin
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QuestionIs it possible to make a Binary for SSRS 2014? Pin
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Questiongetting Failed to get url configuration section. Pin
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QuestionHow to add digital signature to pdf file generated through SSRS custom export option Pin
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QuestionCorrupt zip file on subscriptions Pin
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