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Windows PowerShell Provider Overview


A Windows PowerShell provider allows any data store to be exposed like a file system as if it were a mounted drive. For example, the built-in Registry provider allows you to navigate the registry like you would navigate the c drive of your computer. A provider can also override the Item cmdlets (for example, Get-Item, Set-Item, etc.) such that the data in your data store can be treated like files and directories are treated when navigating a file system. For more information about providers and drives, and the built-in providers in Windows PowerShell, see about_Providers [v4].

A Provider defines the logic that is used to access, navigate, and edit a data store, while a drive specifies a specific entry point to a data store (or a portion of a data store) that is of the type defined by the provider. For example, the Registry provider allows you to access hives and keys in a registry, and the HKLM and HKCU drives specify the corresponding hives within the registry. The HKLM and HKCU drives both use the Registry provider.

When you write a provider, you can specify default drives—drives that are created automatically when the provider is available. You also define a method to create new drives that use that provider.

There are several types of providers, each of which provides a different level of functionality. A provider is implemented as a class that derives from one of the descendants of the CmdletProvider class. For information about the different types of providers, see Provider types.

Providers can implement methods that correspond to cmdlets, creating custom behaviors for those cmdlets when used in a drive for that provider. Depending on the type of provider, different sets of cmdlets are available. For a complete list of the cmldets available for customization in providers, see Provider cmdlets.

Users navigate provider drives like file systems. Because of this, they expect the syntax of paths to correspond to the paths used in file system navigation. When a user runs a provider cmdlet, they specify a path to the item to be accessed. The path that is specified can be interpreted in several ways. A provider should support one or more of the following path types.

A drive-qualified path is a combination of the item name, the container and subcontainers in which the item is located, and the Windows PowerShell drive through which the item is accessed. (Drives are defined by the provider that is used to access the data store. This path starts with the drive name followed by a colon (:). For example: get-childitem C:

To allow the Windows PowerShell engine to initialize and uninitialize your provider, the provider must support a provider-qualified path. For example, the user can initialize and uninitialize the FileSystem provider because it defines the following provider-qualified path: FileSystem::\\uncshare\abc\bar.

To allow remote access to your Windows PowerShell provider, it should support a provider-direct path to pass directly to the Windows PowerShell provider for the current location. For example, the registry Windows PowerShell provider can use \\server\regkeypath as a provider-direct path.

To allow the provider cmdlet to access data using non-Windows PowerShell application programming interfaces (APIs), your Windows PowerShell provider should support a provider-internal path. This path is indicated after the "::" in the provider-qualified path. For example, the provider-internal path for the filesystem Windows PowerShell provider is \\uncshare\abc\bar.

The behavior of some provider-specific cmdlets can be overridden by a provider. For a list of parameters that can be overridden, and how to override them in your provider class, see Provider cmdlet parameters

Providers can define dynamic parameters that are added to a provider cmdlet when the user specifies a certain value for one of the static parameters of the cmdlet. A provider does this by implementing one or more dynamic parameter methods. For a list of cmdlet parameters that can be used to add dynamic parameter, and the methods used to implement them, see Provider cmdlet dynamic parameters.

The ProviderCapabilities enumeration defines a number of capabilities that providers can support. These include the ability to use wildcards, filter items, and support transactions. To specify capabilities for a provider, add a list of values of the ProviderCapabilities enumeration, combined with a logical OR operation, as the ProviderCapabilities property (the second parameter of the attribute) of the CmdletProviderAttribute attribute for your provider class. For example, the following attribute specifies that the provider supports the ShouldProcess and Transactions capabilities.

[CmdletProvider(RegistryProvider.ProviderName, ProviderCapabilities.ShouldProcess | ProviderCapabilities.Transactions)]

When writing a provider, you can implement your own Help for the provider cmdlets that you support. This includes a single help topic for each provider cmdlet or multiple versions of a help topic for cases where the provider cmdlet acts differently based on the use of dynamic parameters. To support provider cmdlet-specific help, your provider must implement the ICmdletProviderSupportsHelp interface.

The Windows PowerShell engine calls the GetHelpMaml method to display the Help topic for your provider cmdlets. The engine provides the name of the cmdlet that the user specified when running the Get-Help cmdlet and the current path of the user. The current path is required if your provider implements different versions of the same provider cmdlet for different drives. The method must return a string that contains the XML for the cmdlet Help.

The content for the Help file is written using PSMAML XML. This is the same XML schema that is used for writing Help content for stand-alone cmdlets. Add the content for your custom cmdlet Help to the Help file for your provider under the CmdletHelpPaths element. The following example shows the command element for a single provider cmdlet, and it shows how you specify the name of the provider cmdlet that your provider. supports