Add a file upload component

[mkArtakMSFT]

Introduce a component for file upload. We have a couple of examples of this including @SteveSandersonMS's sample here: http://blog.stevensanderson.com/2019/09/13/blazor-inputfile/

[RemiBou]

It would be easier if there was a class that would handle the js interop. It's 20 LOC but I think it would be easier for everybody to have this built in instead of relying on 3rd party lib. I am not a big fan of builtin JS interop (like a full DOM interaction wrapper), but in this case it would be nice.

[conficient]

Agreed @RemiBou - I liked your blog article on this, by the way 🥇

This is almost "core" functionality and a lot of apps will want to do this, so it would be nice if there was a <UploadFile> component and the necessary JSinterop was embedded in either blazor.webassembly.js or blazor.server.js as appropriate. That way you don't have to import a package to do this.

It won't suit all use cases but those can be implemented custom packages and JSinterop as required.

[ryanelian]

I love this library approach for uploading files to Blazor:

https://github.com/Tewr/BlazorFileReader

It turns file input into readable stream.

I think you guys can improve upon this concept by automatically streaming the input file into a temporary folder.

<form>
    <!-- File automagically gets uploaded when selected, streamed directly into a temporary file / folder transparently. Allow a progress bar for good measure. -->
    <input type="file" @bind-value="MyFile" @progress="PercentageProgress" />
</form>

@code {
    System.IO.FileStream MyFile { set; get; }
    double PercentageProgress { set; get; }
}

[rynowak]

@SteveSandersonMS also made a thing http://blog.stevensanderson.com/2019/09/13/blazor-inputfile/

[etherealjoy]

@SteveSandersonMS also made a thing http://blog.stevensanderson.com/2019/09/13/blazor-inputfile/

I like this. I hope in the future you can take it forward and make it more intuitive and easy to use.
No fancy setup needed, it just works!