BlazorInputFile - Synchronous reads are not supported

Question

I am trying to use SteveSanderson's BlazorInputFile package to upload files in a Blazor WASM app. (Server/Client setup). I installed the package according to the instructions on his blog post.

My api takes in the file in a byte[] so I am converting the file from a Stream to byte[], and then posting to my API endpoint in the Server.

private async Task Upload(InputFileChangeEventArgs e)
{
    MemoryStream ms = new MemoryStream();
    e.File.OpenReadStream().CopyTo(ms);
    var bytes = ms.ToArray();
    UploadFile file = new UploadFile
    {
        FileName = e.File.Name,
        FileContent = bytes,
        Size = e.File.Size,
        ContentType = e.File.ContentType
    };
        await Http.PostAsJsonAsync<UploadFile>("/api/uploadfile", file);
        await OnInitializedAsync();
}

Unfortunately I keep getting an error/exception from BlazorInputFile which says "Synchronous reads are not supported".

I have tried to search the error and had various fixes (Browser adblocker could be blocking etc) but not of them has fixed the problem.

Answer 1

Looks like the issue is you are using the synchronous version of Stream.CopyTo Method which is the reason you are getting the error message about synchronous reads not being supported. I believe changing that line to:

await e.File.OpenReadStream().CopyToAsync(ms);

Will most likely solve your issue.