Processing a file "uploaded" via <InputFile>

[JasonKoopmans]

Is it possible to save a file that's "uploaded" through the <InputFile /> component and wind up saving it through the FileAPI implemented in your library? I see references to Blob and File -- but it isn't clear if those are translatable to the IBrowserFile interface thats available when the onchange event fires on the InputFile.

Consider:

<InputFile   OnChange="@OnChange" />

Which is handled by:

public void OnChange(InputFileChangeEventArgs args) {
  // file implements IBrowserFile, which contains OpenReadStream()
  var file = args.File

}

[KristofferStrube]

Thanks for the issue. I will try to explore this issue more closely.

My first bet would be that it is not directly possible, but we could probably read the content of the file as a string or byte array and then create a new Blob using some custom JSInterop and parse that to the library through the CreateAsync method on the Blob class.

[KristofferStrube]

I have now constructed an example that shows how to use them together.

@page "/InputFileExample"
@inject FileSystemAccessService FileSystemAccessService

<PageTitle>InputFile Example</PageTitle>

<InputFile OnChange="OnChange" />
<br />
@if (buffer is not null)
{
    <button @onclick="Save">Save</button>
}

@code {
    public byte[] buffer;

    public async Task OnChange(InputFileChangeEventArgs args)
    {
        var file = args.File;
        using var stream = file.OpenReadStream();
        buffer = new byte[stream.Length];
        await stream.ReadAsync(buffer);
    }

    public async Task Save()
    {
        var fileHandle = await FileSystemAccessService.ShowSaveFilePickerAsync();
        var writable = await fileHandle.CreateWritableAsync();
        await writable.WriteAsync(BytesToString(buffer));
        await writable.CloseAsync();
    }

    private static string BytesToString(byte[] bytes)
    {
        using MemoryStream stream = new MemoryStream(bytes);
        using StreamReader streamReader = new StreamReader(stream);
        return streamReader.ReadToEnd();
    }
}

The example can also be seen here: https://kristofferstrube.github.io/Blazor.FileSystemAccess/InputFileExample

It is not the most beautiful thing and I think a way that could makes this nicer would be if the FileSystemWritableFileStream where to extend the Stream class and override some of its methods like others have suggested earlier. I will keep this issue open to track progress on that.

• [x] Make FileSystemWritableFileStream extend Stream

[JasonKoopmans]

Thanks for sharing this. FileSystemWritableFileStream extending Stream would would be convenient. This example works for small files, but this needs to load the files completely into memory which would be a problem for larger files