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title	author	description	monikerRange	ms.author	ms.custom	ms.date	uid
File Providers in ASP.NET Core	guardrex	Learn how ASP.NET Core abstracts file system access through the use of File Providers.	>= aspnetcore-2.1	riande	mvc	08/26/2019	fundamentals/file-providers

File Providers in ASP.NET Core

By Steve Smith and Luke Latham

::: moniker range=">= aspnetcore-3.0"

ASP.NET Core abstracts file system access through the use of File Providers. File Providers are used throughout the ASP.NET Core framework:

IWebHostEnvironment exposes the app's content root and web root as IFileProvider types.
Static File Middleware uses File Providers to locate static files.
Razor uses File Providers to locate pages and views.
.NET Core tooling uses File Providers and glob patterns to specify which files should be published.

View or download sample code (how to download)

File Provider interfaces

The primary interface is xref:Microsoft.Extensions.FileProviders.IFileProvider. IFileProvider exposes methods to:

Obtain file information (xref:Microsoft.Extensions.FileProviders.IFileInfo).
Obtain directory information (xref:Microsoft.Extensions.FileProviders.IDirectoryContents).
Set up change notifications (using an xref:Microsoft.Extensions.Primitives.IChangeToken).

IFileInfo provides methods and properties for working with files:

You can read from the file using the IFileInfo.CreateReadStream method.

The sample app demonstrates how to configure a File Provider in Startup.ConfigureServices for use throughout the app via dependency injection.

File Provider implementations

Three implementations of IFileProvider are available.

Implementation	Description
PhysicalFileProvider	The physical provider is used to access the system's physical files.
ManifestEmbeddedFileProvider	The manifest embedded provider is used to access files embedded in assemblies.
CompositeFileProvider	The composite provider is used to provide combined access to files and directories from one or more other providers.

PhysicalFileProvider

The xref:Microsoft.Extensions.FileProviders.PhysicalFileProvider provides access to the physical file system. PhysicalFileProvider uses the xref:System.IO.File?displayProperty=fullName type (for the physical provider) and scopes all paths to a directory and its children. This scoping prevents access to the file system outside of the specified directory and its children. The most common scenario for creating and using a PhysicalFileProvider is to request an IFileProvider in a constructor through dependency injection.

When instantiating this provider directly, a directory path is required and serves as the base path for all requests made using the provider.

The following code shows how to create a PhysicalFileProvider and use it to obtain directory contents and file information:

var provider = new PhysicalFileProvider(applicationRoot);
var contents = provider.GetDirectoryContents(string.Empty);
var fileInfo = provider.GetFileInfo("wwwroot/js/site.js");

Types in the preceding example:

provider is an IFileProvider.
contents is an IDirectoryContents.
fileInfo is an IFileInfo.

The File Provider can be used to iterate through the directory specified by applicationRoot or call GetFileInfo to obtain a file's information. The File Provider has no access outside of the applicationRoot directory.

The sample app creates the provider in the app's Startup.ConfigureServices class using IHostingEnvironment.ContentRootFileProvider:

var physicalProvider = _env.ContentRootFileProvider;

ManifestEmbeddedFileProvider

The xref:Microsoft.Extensions.FileProviders.ManifestEmbeddedFileProvider is used to access files embedded within assemblies. The ManifestEmbeddedFileProvider uses a manifest compiled into the assembly to reconstruct the original paths of the embedded files.

Add a package reference to the project for the Microsoft.Extensions.FileProviders.Embedded package.

To generate a manifest of the embedded files, set the <GenerateEmbeddedFilesManifest> property to true. Specify the files to embed with <EmbeddedResource>:

[!code-csharp]

Use glob patterns to specify one or more files to embed into the assembly.

The sample app creates an ManifestEmbeddedFileProvider and passes the currently executing assembly to its constructor.

Startup.cs:

var manifestEmbeddedProvider = 
    new ManifestEmbeddedFileProvider(Assembly.GetEntryAssembly());

Additional overloads allow you to:

Specify a relative file path.
Scope files to a last modified date.
Name the embedded resource containing the embedded file manifest.

Overload	Description
`ManifestEmbeddedFileProvider(Assembly, String)`	Accepts an optional `root` relative path parameter. Specify the `root` to scope calls to xref:Microsoft.Extensions.FileProviders.IFileProvider.GetDirectoryContents* to those resources under the provided path.
`ManifestEmbeddedFileProvider(Assembly, String, DateTimeOffset)`	Accepts an optional `root` relative path parameter and a `lastModified` date (xref:System.DateTimeOffset) parameter. The `lastModified` date scopes the last modification date for the xref:Microsoft.Extensions.FileProviders.IFileInfo instances returned by the xref:Microsoft.Extensions.FileProviders.IFileProvider.
`ManifestEmbeddedFileProvider(Assembly, String, String, DateTimeOffset)`	Accepts an optional `root` relative path, `lastModified` date, and `manifestName` parameters. The `manifestName` represents the name of the embedded resource containing the manifest.

CompositeFileProvider

The xref:Microsoft.Extensions.FileProviders.CompositeFileProvider combines IFileProvider instances, exposing a single interface for working with files from multiple providers. When creating the CompositeFileProvider, pass one or more IFileProvider instances to its constructor.

In the sample app, a PhysicalFileProvider and a ManifestEmbeddedFileProvider provide files to a CompositeFileProvider registered in the app's service container:

[!code-csharp]

Watch for changes

The IFileProvider.Watch method provides a scenario to watch one or more files or directories for changes. Watch accepts a path string, which can use glob patterns to specify multiple files. Watch returns an xref:Microsoft.Extensions.Primitives.IChangeToken. The change token exposes:

xref:Microsoft.Extensions.Primitives.IChangeToken.HasChanged – A property that can be inspected to determine if a change has occurred.
xref:Microsoft.Extensions.Primitives.IChangeToken.RegisterChangeCallback* – Called when changes are detected to the specified path string. Each change token only calls its associated callback in response to a single change. To enable constant monitoring, use a xref:System.Threading.Tasks.TaskCompletionSource`1 (shown below) or recreate IChangeToken instances in response to changes.

In the sample app, the WatchConsole console app is configured to display a message whenever a text file is modified:

[!code-csharp]

Some file systems, such as Docker containers and network shares, may not reliably send change notifications. Set the DOTNET_USE_POLLING_FILE_WATCHER environment variable to 1 or true to poll the file system for changes every four seconds (not configurable).

Glob patterns

File system paths use wildcard patterns called glob (or globbing) patterns. Specify groups of files with these patterns. The two wildcard characters are * and **:

*
Matches anything at the current folder level, any filename, or any file extension. Matches are terminated by / and . characters in the file path.

**
Matches anything across multiple directory levels. Can be used to recursively match many files within a directory hierarchy.

Glob pattern examples

directory/file.txt
Matches a specific file in a specific directory.

directory/*.txt
Matches all files with .txt extension in a specific directory.

directory/*/appsettings.json
Matches all appsettings.json files in directories exactly one level below the directory folder.

directory/**/*.txt
Matches all files with .txt extension found anywhere under the directory folder.

::: moniker-end

::: moniker range="< aspnetcore-3.0"

ASP.NET Core abstracts file system access through the use of File Providers. File Providers are used throughout the ASP.NET Core framework:

xref:Microsoft.Extensions.Hosting.IHostingEnvironment exposes the app's content root and web root as IFileProvider types.
Static File Middleware uses File Providers to locate static files.
Razor uses File Providers to locate pages and views.
.NET Core tooling uses File Providers and glob patterns to specify which files should be published.

View or download sample code (how to download)

File Provider interfaces

The primary interface is xref:Microsoft.Extensions.FileProviders.IFileProvider. IFileProvider exposes methods to:

Obtain file information (xref:Microsoft.Extensions.FileProviders.IFileInfo).
Obtain directory information (xref:Microsoft.Extensions.FileProviders.IDirectoryContents).
Set up change notifications (using an xref:Microsoft.Extensions.Primitives.IChangeToken).

IFileInfo provides methods and properties for working with files:

You can read from the file using the IFileInfo.CreateReadStream method.

The sample app demonstrates how to configure a File Provider in Startup.ConfigureServices for use throughout the app via dependency injection.

File Provider implementations

Three implementations of IFileProvider are available.

Implementation	Description
PhysicalFileProvider	The physical provider is used to access the system's physical files.
ManifestEmbeddedFileProvider	The manifest embedded provider is used to access files embedded in assemblies.
CompositeFileProvider	The composite provider is used to provide combined access to files and directories from one or more other providers.

PhysicalFileProvider

When instantiating this provider directly, a directory path is required and serves as the base path for all requests made using the provider.

The following code shows how to create a PhysicalFileProvider and use it to obtain directory contents and file information:

var provider = new PhysicalFileProvider(applicationRoot);
var contents = provider.GetDirectoryContents(string.Empty);
var fileInfo = provider.GetFileInfo("wwwroot/js/site.js");

Types in the preceding example:

provider is an IFileProvider.
contents is an IDirectoryContents.
fileInfo is an IFileInfo.

The sample app creates the provider in the app's Startup.ConfigureServices class using IHostingEnvironment.ContentRootFileProvider:

var physicalProvider = _env.ContentRootFileProvider;

ManifestEmbeddedFileProvider

To generate a manifest of the embedded files, set the <GenerateEmbeddedFilesManifest> property to true. Specify the files to embed with <EmbeddedResource>:

[!code-csharp]

Use glob patterns to specify one or more files to embed into the assembly.

The sample app creates an ManifestEmbeddedFileProvider and passes the currently executing assembly to its constructor.

Startup.cs:

var manifestEmbeddedProvider = 
    new ManifestEmbeddedFileProvider(Assembly.GetEntryAssembly());

Additional overloads allow you to:

Specify a relative file path.
Scope files to a last modified date.
Name the embedded resource containing the embedded file manifest.

Overload	Description
`ManifestEmbeddedFileProvider(Assembly, String)`	Accepts an optional `root` relative path parameter. Specify the `root` to scope calls to xref:Microsoft.Extensions.FileProviders.IFileProvider.GetDirectoryContents* to those resources under the provided path.
`ManifestEmbeddedFileProvider(Assembly, String, DateTimeOffset)`	Accepts an optional `root` relative path parameter and a `lastModified` date (xref:System.DateTimeOffset) parameter. The `lastModified` date scopes the last modification date for the xref:Microsoft.Extensions.FileProviders.IFileInfo instances returned by the xref:Microsoft.Extensions.FileProviders.IFileProvider.
`ManifestEmbeddedFileProvider(Assembly, String, String, DateTimeOffset)`	Accepts an optional `root` relative path, `lastModified` date, and `manifestName` parameters. The `manifestName` represents the name of the embedded resource containing the manifest.

CompositeFileProvider

In the sample app, a PhysicalFileProvider and a ManifestEmbeddedFileProvider provide files to a CompositeFileProvider registered in the app's service container:

[!code-csharp]

Watch for changes

xref:Microsoft.Extensions.Primitives.IChangeToken.HasChanged – A property that can be inspected to determine if a change has occurred.
xref:Microsoft.Extensions.Primitives.IChangeToken.RegisterChangeCallback* – Called when changes are detected to the specified path string. Each change token only calls its associated callback in response to a single change. To enable constant monitoring, use a xref:System.Threading.Tasks.TaskCompletionSource`1 (shown below) or recreate IChangeToken instances in response to changes.

In the sample app, the WatchConsole console app is configured to display a message whenever a text file is modified:

[!code-csharp]

Glob patterns

File system paths use wildcard patterns called glob (or globbing) patterns. Specify groups of files with these patterns. The two wildcard characters are * and **:

*
Matches anything at the current folder level, any filename, or any file extension. Matches are terminated by / and . characters in the file path.

**
Matches anything across multiple directory levels. Can be used to recursively match many files within a directory hierarchy.

Glob pattern examples

directory/file.txt
Matches a specific file in a specific directory.

directory/*.txt
Matches all files with .txt extension in a specific directory.

directory/*/appsettings.json
Matches all appsettings.json files in directories exactly one level below the directory folder.

directory/**/*.txt
Matches all files with .txt extension found anywhere under the directory folder.

::: moniker-end

19 KiB Raw Blame History Unescape Escape

File Providers in ASP.NET Core

File Provider interfaces

File Provider implementations

PhysicalFileProvider

ManifestEmbeddedFileProvider

CompositeFileProvider

Watch for changes

Glob patterns

File Provider interfaces

File Provider implementations

PhysicalFileProvider

ManifestEmbeddedFileProvider

CompositeFileProvider

Watch for changes

Glob patterns

19 KiB

Raw Blame History