Introduction

A Blazor wrapper for the browser API File System Access

The API makes it possible to read and write to your local file system from the browser both files and directories. The API is supported on a limited set of browsers. Most noticeable not supported on Chrome for Android phones yet nor browsers on Apple mobile products.

Demo

The sample project can be demoed at https://kristofferstrube.github.io/Blazor.FileSystemAccess/

On each page you can find the corresponding code for the example in the top right corner.

On the main page you can see if the API has at least minimal support in the used browser.

Getting Started

Prerequisites

You need to install .NET 6.0 or newer to use the library.

Download .NET 6

Installation

You can install the package via Nuget with the Package Manager in your IDE or alternatively using the command line:

dotnet add package KristofferStrube.Blazor.FileSystemAccess

Usage

The package can be used in Blazor WebAssembly projects.

Import

You also need to reference the package in order to use it in your pages. This can be done in _Import.razor by adding the following.

@using KristofferStrube.Blazor.FileSystemAccess

Add to service collection

An easy way to make the service available in all your pages is by registering it in the IServiceCollection so that it can be dependency injected in the pages that need it. This is done in Program.cs by adding the following before you build the host and run it.

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

// Other services are added.

builder.Services.AddFileSystemAccessService();

await builder.Build().RunAsync();

Inject in page

Then the service can be injected in a page like so:

@inject FileSystemAccessService FileSystemAccessService;

Then you can use FileSystemAccessService to open one of the three dialogs available in the FileSystemAccess API like this:

<button @onclick="OpenAndReadFile">Open File Picker for Single File and Read</button>
<br />
@Text

@code {
    private string Text = "";

    private async Task OpenAndReadFile()
    {
        FileSystemFileHandle? fileHandle = null;
        try
        {
            OpenFilePickerOptionsStartInWellKnownDirectory options = new()
                {
                    Multiple = false,
                    StartIn = WellKnownDirectory.Downloads
                };
            var fileHandles = await FileSystemAccessService.ShowOpenFilePickerAsync(options);
            fileHandle = fileHandles.Single();
        }
        catch (JSException ex)
        {
            // Handle Exception or cancelation of File Access prompt
            Console.WriteLine(ex);
        }
        finally
        {
            if (fileHandle is not null)
            {
                var file = await fileHandle.GetFileAsync();
                Text = await file.TextAsync();
                StateHasChanged();
            }
        }
    }
}

Issues

Feel free to open issues on the repository if you find any errors with the package or have wishes for features.

Related articles

This repository was build with inspiration and help from the following series of articles:

• Wrapping JavaScript libraries in Blazor WebAssembly/WASM
• Call anonymous C# functions from JS in Blazor WASM
• Using JS Object References in Blazor WASM to wrap JS libraries
• Blazor WASM 404 error and fix for GitHub Pages
• How to fix Blazor WASM base path problems