Blazor.SeekableStream 1.0.1

A Stream interop for Blazor from Javascript to .NET that supports Seek operations (as well as Position property). By default, Blazor's IJSStreamReference does not support Seek method and throws NotSupportedException.

Installation

Install the NuGet package Blazor.SeekableStream to your Blazor project.

dotnet add package Blazor.SeekableStream

Usage

See also: the Demo project.

Get a hold to a Javascript's ArrayBuffer, Blob or Response object and pass it to .NET as the usual IJSObjectReference.

For example, this function send a File (which is a Blob) that the user picked:

interop.js:

export function pickFileAsync() {
    return new Promise(r => {
        const txt = document.createElement("input");
        txt.type = "file";
        txt.onchange = () => r(txt.files[0]);
        txt.click();
    });
}

Then in .NET, call AsSeekableStreamReference on the appropriate IJSObjectReference instances. You need to pass an IJSRuntime instance as the parameter as well.

Index.razor.cs:

var mod = await Js.InvokeAsync<IJSObjectReference>(
    "import",
    "/interop.js");

var file = await mod.InvokeAsync<IJSObjectReference>(PickMethodName);
var seekable = file.AsSeekableStreamReference(Js);
var stream = await seekable.OpenReadStreamAsync();

// Work with Stream