Writing a custom file system provider

The CMS.IO library allows you to customize Kentico to support a file system of your choice. As described in the Overview page, you can achieve this by developing a custom provider based on the classes contained within CMS.IO.


To implement a custom file system provider, you need to add a new assembly to the Kentico solution:

  1. Open your Kentico solution in Visual Studio.

  2. Add a new Class Library project to the Kentico solution, for example named CustomFileSystemProvider.

  3. Add references to the required Kentico libraries (DLLs) for the new project:

    1. Right-click the project and select Add -> Reference.

    2. Select the Browse tab of the Reference manager dialog, click Browse and navigate to the Lib folder of your Kentico web project.

    3. Add references to the following libraries:

      • CMS.Base.dll
      • CMS.Core.dll
      • CMS.DataEngine.dll
      • CMS.Helpers.dll
      • CMS.IO.dll
  4. Reference the CustomFileSystemProvider project from the Kentico web project (CMSApp or CMS).

The Kentico installation directory contains sample definitions of all classes required to implement a generic file system provider. To help with the implementation, you can copy these classes into the custom file system provider’s project:

  1. Open your Kentico program files directory (by default C:\Program Files\Kentico\<version>).
  2. Expand the CodeSamples\CustomizationSamples\CustomFileSystemProvider subfolder.
  3. Copy all contained files into the CustomFileSystemProvider directory in your web project.
  4. Include the new files into the CustomFileSystemProvider project in Visual Studio:
    1. Expand the CustomFileSystemProvider project in the Solution Explorer.
    2. Click Show all files at the top of the Solution Explorer.
    3. Select the new files while holding the Ctrl key.
    4. Right-click one of the files and select Include in Project.
  5. Edit the copied files and rename the namespaces to exactly match the assembly name of your custom project (CustomFileSystemProvider in this example).


If you choose to take advantage of the prepared classes, go through all files contained in the project and replace the NotImplementedExceptions inside methods with your implementation, and implement property and method overrides. You can consult the following steps for reference or if you wish to create a provider from scratch.

  1. Create two separate classes that inherit from the following abstract classes:

    • CMS.IO.AbstractDirectory
    • CMS.IO.AbstractFile
  2. Implement all methods defined in the abstract classes.

  3. Create three other classes that inherit from the following classes:

    • CMS.IO.DirectoryInfo
    • CMS.IO.FileInfo
    • CMS.IO.FileStream
  4. Override all methods and properties from those classes.

  5. Create constructors for the classes listed in step 3 according to the following table:

    Inherits from



    public DirectoryInfo(string path)


    public FileInfo(string filename)


    public FileStream(string path, CMS.IO.FileMode mode)

    public FileStream(string path, CMS.IO.FileMode mode, CMS.IO.FileAccess access)

    public FileStream(string path, CMS.IO.FileMode mode, CMS.IO.FileAccess access, CMS.IO.FileShare share)

    public FileStream(string path, CMS.IO.FileMode mode, CMS.IO.FileAccess access, CMS.IO.FileShare share, int bSize)

Note: The custom file system provider classes must be placed into a namespace that exactly matches the name of the given assembly.


Perform the following configuration steps to start using your custom file system provider:

  1. Add the CMSStorageProviderAssembly key to the appSettings section of your project’s web.config file. Set the key’s value to the assembly name of your custom provider.

  2. Configure the project to use the provider. Choose between the following options:

    • Add the CMSExternalStorageName key to the appSettings section of the web.config file and set the value to any identifier. This maps the project’s entire file system to the custom provider.

      – OR –

    • Use the API to create an instance of the CMS.IO.StorageProvider class and map specific project folders to your custom provider.


  • The following web.config keys configure the application to store its entire file system using a custom provider implemented in the “CustomFileSystemProvider” assembly with “custom” as the identifier:

        <add key="CMSStorageProviderAssembly" value="CustomFileSystemProvider" />
        <add key="CMSExternalStorageName" value="custom" />
  • The following code registers a module that maps a site’s media library folder to a custom storage provider:

      using CMS;
      using CMS.Base;
      using CMS.DataEngine;
      using CMS.IO;
      // Registers the custom module into the system
      [assembly: RegisterModule(typeof(CustomInitializationModule))]
      public class CustomInitializationModule : Module
          // Module class constructor, the system registers the module under the name "CustomInit"
          public CustomInitializationModule()
              : base("CustomInit")
          // Contains initialization code that is executed when the application starts
          protected override void OnInit()
              // Creates a new StorageProvider instance using the custom 'CustomFileSystemProvider' assembly
              var customMediaProvider = new StorageProvider("custom", "CustomFileSystemProvider");
              // Maps a directory to the provider
              StorageHelper.MapStoragePath("~/MySite/Media/", customMediaProvider);

    To create an instance of the StorageProvider class for your custom file system provider, call the constructor with the following parameters:

    1. The provider’s external storage name. Can be an empty string for providers that use the local file system, or any string except azure or amazon for external providers. The value is assigned to the ExternalStorageName property of the StorageProvider class.
    2. The name of the code assembly containing the provider’s implementation.
    3. (Optional) A bool parameter that specifies whether the storage is shared.For more information about storage provider mapping options, see: Configuring file system providers