Telerik.Blazor.Components.FileSelect.Stream Invalid operation exception

[bimal]

Hi folks,

I am trying to upload a file to a state container using the FileSelect component.

private async Task OnFileSelected(FileSelectEventArgs e)
{
try
{
foreach (var file in e.Files)
{

using var memoryStream = new MemoryStream();

byte[] buffer = new byte[81920]; // 80 KB buffer size
int bytesRead;

while ((bytesRead = await file.Stream.ReadAsync(buffer, 0, buffer.Length)) > 0)
{
await memoryStream.WriteAsync(buffer, 0, bytesRead);
}

byte[] fileBytes = memoryStream.ToArray();

// Store file in state container
await FileState.AddFileContentAsync(file.Name, fileBytes);

}

}
catch(Exception ex)
{
Console.WriteLine("Error uploading files " + ex.Message);

}

StateHasChanged();
}
Here file.Stream.ReadAsync is not working. 
In Visual studio for the file.Steam property I am getting the following error message.

SYNCHRONOUS_FILESTREAM_READ_ERROR property
Synchronous actions on the file stream is not supported by the Blazor framework in Blazor Server-side apps due to the SignalR communication between the client and the host. Use the 'ReadAsync' method instead.

and the code does not continue to execute after the line  while ((bytesRead = await file.Stream.ReadAsync(buffer, 0, buffer.Length)) > 0) 

[bimal]

Hi Anislav ,

Issue fixed. 

In Program.cs had to increase the SignalR MaximumMessageReceiveSize to about 1 mb from default 32 kb.

builder.Services.AddServerSideBlazor()
    .AddHubOptions(options =>
    {
        options.MaximumReceiveMessageSize = 1 * 1024 * 1024;
    });

[Anislav]

Did you try using CopyToAsync instead of ReadAsync? Here's an example specifically for Blazor Server apps: https://www.telerik.com/blazor-ui/documentation/components/fileselect/events#example .

Regards,
Anislav Atanasov

[bimal]

Yes Anislav,

I tried the standard code first as shown below, since it was not working.
I tried a workaround with ReadAsync . it was also giving the same error 

private async Task OnFileSelected(FileSelectEventArgs e)
{
foreach (var file in e.Files)
{
using var stream = new MemoryStream();
await file.Stream.CopyToAsync(stream);
byte[] fileBytes = stream.ToArray();

// Store file in state container
await FileState.AddFileContentAsync(file.Name, fileBytes);
}
StateHasChanged();
}