BlazorDownloadFile

Blazor download files to the browser from c# without any JavaScript library or dependency.
BlazorDownloadFile is the solution to saving files on the client-side, and is perfect for web apps that generates files on the client.
However if the file is coming from the server we recommend you to first try to use Content-Disposition attachment response header as it has more cross-browser compatibility.
Installation

Install-Package BlazorDownloadFile -Version 2.4.0.2
Register the service in your services method

services.AddBlazorDownloadFile(ServiceLifetime lifetime = ServiceLifetime.Scoped);
Note: ServiceLifetime.Singleton is not supported.
No javascript library reference dependency unless...

If you are using Content-Security-Policy "script-src 'self'" then you need to add the script manually:

<script src="_content/BlazorDownloadFile/BlazorDownloadFileScript.js"><script>

Usage

[Inject] IBlazorDownloadFileService BlazorDownloadFileService { get; set; }
BlazorDownloadFileService Methods

/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytesBase64">The base 64 string</param>
/// <returns></returns>
ValueTask AddBuffer(string bytesBase64);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytesBase64">The base 64 string</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <returns></returns>
ValueTask AddBuffer(string bytesBase64, CancellationToken cancellationToken);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytesBase64">The base 64 string</param>
/// <param name="timeOut">The timeout</param>
/// <returns></returns>
ValueTask AddBuffer(string bytesBase64, TimeSpan timeOut);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytes">The bytes</param>
/// <returns></returns>
ValueTask AddBuffer(byte[] bytes);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytes">The bytes</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <returns></returns>
ValueTask AddBuffer(byte[] bytes, CancellationToken cancellationToken);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytes">The bytes</param>
/// <param name="timeOut">The timeout</param>
/// <returns></returns>
ValueTask AddBuffer(byte[] bytes, TimeSpan timeOut);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytes">The bytes</param>
/// <returns></returns>
ValueTask AddBuffer(IEnumerable<byte> bytes);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytes">The bytes</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <returns></returns>
ValueTask AddBuffer(IEnumerable<byte> bytes, CancellationToken cancellationToken);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="bytes">The bytes</param>
/// <param name="timeOut">The timeout</param>
/// <returns></returns>
ValueTask AddBuffer(IEnumerable<byte> bytes, TimeSpan timeOut);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="stream">The stream</param>
/// <returns></returns>
ValueTask AddBuffer(Stream stream);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="stream">The stream</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <returns></returns>
ValueTask AddBuffer(Stream stream, CancellationToken cancellationToken);
/// <summary>
/// Adds a buffer to javascript side
/// </summary>
/// <param name="stream">The stream</param>
/// <param name="streamReadcancellationToken">The cancellation token</param>
/// <param name="timeOutJavaScript">The timeout</param>
/// <returns></returns>
ValueTask AddBuffer(Stream stream, CancellationToken streamReadcancellationToken, TimeSpan timeOutJavaScript);
/// <summary>
/// Checks wether there is any buffer loaded in the JavaScript side.
/// </summary>
/// <returns></returns>
ValueTask<bool> AnyBuffer();
/// <summary>
/// Gets the buffers count loaded in the JavaScript side.
/// </summary>
/// <returns></returns>
ValueTask<int> BuffersCount();
/// <summary>
/// Clears the buffers in javascript side
/// </summary>
/// <returns></returns>
ValueTask ClearBuffers();
/// <summary>
/// Merges and downloads all pending buffers into a single file in the browser. This method should be called when the added buffers where a base64 string type. 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="contentType">The content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadBase64Buffers(string fileName, string contentType = "application/octet-stream");
/// <summary>
/// Merges and downloads all pending buffers into a single file in the browser. This method should be called when the added buffers where a base64 string type. 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="contentType">The content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadBase64Buffers(string fileName, CancellationToken cancellationToken, string contentType = "application/octet-stream");
/// <summary>
/// Merges and downloads all pending buffers into a single file in the browser. This method should be called when the added buffers where a base64 string type. 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="timeOut">The timeout</param>
/// <param name="contentType">The content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadBase64Buffers(string fileName, TimeSpan timeOut, string contentType = "application/octet-stream");
/// <summary>
/// Merges and downloads all pending buffers into a single file in the browser. This method should be called when the added buffers where a byte array, byte enumerable or a stream types. 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="contentType">The content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadBinaryBuffers(string fileName, string contentType = "application/octet-stream");
/// <summary>
/// Merges and downloads all pending buffers into a single file in the browser. This method should be called when the added buffers where a byte array, byte enumerable or a stream types. 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="contentType">The content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadBinaryBuffers(string fileName, CancellationToken cancellationToken, string contentType = "application/octet-stream");
/// <summary>
/// Merges and downloads all pending buffers into a single file in the browser. This method should be called when the added buffers where a byte array, byte enumerable or a stream types. 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="timeOut">The timeout</param>
/// <param name="contentType">The content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadBinaryBuffers(string fileName, TimeSpan timeOut, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytesBase64">The bytes base 64 of the file</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, string bytesBase64, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytesBase64">The bytes base 64 of the file</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, string bytesBase64, CancellationToken cancellationToken, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytesBase64">The bytes base 64 of the file</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, string bytesBase64, TimeSpan timeOut, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, byte[] bytes, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, byte[] bytes, CancellationToken cancellationToken, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, byte[] bytes, TimeSpan timeOut, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, IEnumerable<byte> bytes, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, IEnumerable<byte> bytes, CancellationToken cancellationToken, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, IEnumerable<byte> bytes, TimeSpan timeOut, string contentType = "application/octet-stream");
/// <summary>
///  Download a file from blazor context to the browser.
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="stream">The stream of the file</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, Stream stream, string contentType = "application/octet-stream");
/// <summary>
///  Download a file from blazor context to the browser.
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="stream">The stream of the file</param>
/// <param name="cancellationTokenBytesRead">The cancellation token when reading bytes</param>
/// <param name="cancellationTokenJavaScriptInterop">The cancellation token when executing javascript</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, Stream stream, CancellationToken cancellationTokenBytesRead, CancellationToken cancellationTokenJavaScriptInterop, string contentType = "application/octet-stream");
/// <summary>
///  Download a file from blazor context to the browser.
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="stream">The stream of the file</param>
/// <param name="cancellationTokenBytesRead">The cancellation token when reading bytes</param>
/// <param name="timeOutJavaScriptInterop">The timeout when executing javascript</param>
/// <param name="contentType">The file content type</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, Stream stream, CancellationToken cancellationTokenBytesRead, TimeSpan timeOutJavaScriptInterop, string contentType = "application/octet-stream");
/// <summary>
/// Download a file from blazor context to the brower
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="plainText">The plain text</param>
/// <param name="encoding">The enconding to use</param>
/// <param name="contentType">The file content type</param>
/// <param name="encoderShouldEmitIdentifier">true to specify that the System.Text.Encoding.GetPreamble method returns a Unicode byte order mark.</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFileFromText(string fileName, string plainText, Encoding encoding, string contentType = "text/plain", bool encoderShouldEmitIdentifier = false);
/// <summary>
/// Download a file from blazor context to the brower
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="plainText">The plain text</param>
/// <param name="encoding">The enconding to use</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="contentType">The file content type</param>
/// <param name="encoderShouldEmitIdentifier">true to specify that the System.Text.Encoding.GetPreamble method returns a Unicode byte order mark.</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFileFromText(string fileName, string plainText, Encoding encoding, CancellationToken cancellationToken, string contentType = "text/plain", bool encoderShouldEmitIdentifier = false);
/// <summary>
/// Download a file from blazor context to the brower
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="plainText">The plain text</param>
/// <param name="encoding">The enconding to use</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="contentType">The file content type</param>
/// <param name="encoderShouldEmitIdentifier">true to specify that the System.Text.Encoding.GetPreamble method returns a Unicode byte order mark.</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFileFromText(string fileName, string plainText, Encoding encoding, TimeSpan timeOut, string contentType = "text/plain", bool encoderShouldEmitIdentifier = false);
/// <summary>
/// Download a file from blazor context to the browser 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytesBase64">The bytes base 64 of the file</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, string bytesBase64, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytesBase64">The bytes base 64 of the file</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, string bytesBase64, CancellationToken cancellationToken, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser 
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytesBase64">The bytes base 64 of the file</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, string bytesBase64, TimeSpan timeOut, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, byte[] bytes, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, byte[] bytes, CancellationToken cancellationToken, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, byte[] bytes, TimeSpan timeOut, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, IEnumerable<byte> bytes, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, IEnumerable<byte> bytes, CancellationToken cancellationToken, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the browser
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="bytes">The bytes of the file</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, IEnumerable<byte> bytes, TimeSpan timeOut, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
///  Download a file from blazor context to the browser. Please take note that this method doesn't reset the stream position to 0.
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="stream">The stream of the file</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, Stream stream, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
///  Download a file from blazor context to the browser. Please take note that this method doesn't reset the stream position to 0.
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="stream">The stream of the file</param>
/// <param name="cancellationTokenBytesRead">The cancellation token when reading bytes</param>
/// <param name="cancellationTokenJavaScriptInterop">The cancellation token when executing javascript</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, Stream stream, CancellationToken cancellationTokenBytesRead, CancellationToken cancellationTokenJavaScriptInterop, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
///  Download a file from blazor context to the browser. Please take note that this method doesn't reset the stream position to 0.
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="stream">The stream of the file</param>
/// <param name="cancellationTokenBytesRead">The cancellation token when reading bytes</param>
/// <param name="timeOutJavaScriptInterop">The timeout when executing javascript</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFile(string fileName, Stream stream, CancellationToken cancellationTokenBytesRead, TimeSpan timeOutJavaScriptInterop, int bufferSize = 32768, string contentType = "application/octet-stream", IProgress<double>? progress = null);
/// <summary>
/// Download a file from blazor context to the brower
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="plainText">The plain text</param>
/// <param name="encoding">The enconding to use</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <param name="encoderShouldEmitIdentifier">true to specify that the System.Text.Encoding.GetPreamble method returns a Unicode byte order mark.</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFileFromText(string fileName, string plainText, Encoding encoding, int bufferSize = 32768, string contentType = "text/plain", IProgress<double>? progress = null, bool encoderShouldEmitIdentifier = false);
/// <summary>
/// Download a file from blazor context to the brower
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="plainText">The plain text</param>
/// <param name="encoding">The enconding to use</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <param name="encoderShouldEmitIdentifier">true to specify that the System.Text.Encoding.GetPreamble method returns a Unicode byte order mark.</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFileFromText(string fileName, string plainText, Encoding encoding, CancellationToken cancellationToken, int bufferSize = 32768, string contentType = "text/plain", IProgress<double>? progress = null, bool encoderShouldEmitIdentifier = false);
/// <summary>
/// Download a file from blazor context to the brower
/// </summary>
/// <param name="fileName">The filename</param>
/// <param name="plainText">The plain text</param>
/// <param name="encoding">The enconding to use</param>
/// <param name="timeOut">The timeout of the operation</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="contentType">The file content type</param>
/// <param name="progress">The progress percent of data transfered</param>
/// <param name="encoderShouldEmitIdentifier">true to specify that the System.Text.Encoding.GetPreamble method returns a Unicode byte order mark.</param>
/// <returns></returns>
ValueTask<DownloadFileResult> DownloadFileFromText(string fileName, string plainText, Encoding encoding, TimeSpan timeOut, int bufferSize = 32768, string contentType = "text/plain", IProgress<double>? progress = null, bool encoderShouldEmitIdentifier = false);
Performance Considerations and Understandings

Regarding on some performance test I have done in this library is that, base64 string and byte[] performs faster than Stream always.
Since there is not direct conversion between from c# Stream to a JavaScript object its a little more expensive this task.
When its base64 this is the most simple data type to transfer and work with it.
byte[] gets transformed into base64 string when transfered to JavaScript and for some reason it won't work properly when encoding cause its base64 representation turns to be something else when going after the second partition when gets encoded to base64 string. (If anyone knows how to fix or workaround this make a pull request)
Based on the las sentence, a list of bytes gets passed down from c# to JavaScript as an array of intergers with the bytes representation on JavaScript and this is the reason why I send a IList<byte> rather than byte[] internally to JavaScript.
The binary representation seems to perform very well since we just needed to call Uint8Array and push the binary representation entirely into the array to then pass it down to the JavaScript native Blob object.
Take note that you may use the overload methods with buffers if you are sending big files over the wire and also that browsers have their own limitations on JavaScript Max Blob Size based on the device hardware, browser vendor and the OS.
Take note also that blazor server side uses Signal R and has its data transfer (buffer) limitations.