blazor-docs/knowledge-base/fileselect-autofac.md

title	description	type	page_title	slug	tags	ticketid	res_type
FileSelect ReadAsync Method Throws JsonException	Learn how to resolve an exception about JSON serialization attempting to deserialize an unexpected byte array when using the Telerik Blazor FileSelect.	troubleshooting	FileSelect ReadAsync Method Throws JsonException	fileselect-kb-autofac	telerik, blazor, fileselect, autofac, dependency injection	1637702, 1634460, 1634313, 1632874	kb

Environment

Product	FileSelect for Blazor
Version	5.0.0 and above

Description

This knowledge base article deals with the following issues:

• The FileSelect component's file stream ReadAsync method throws Microsoft.JSInterop.JSException.
• FileSelect file stream reading fails when using builder.Host.UseServiceProviderFactory.
• An exception occurs when trying to upload files through Blazor FileSelect with Autofac dependency injection enabled.

Error Message

Microsoft.JSInterop.JSException: JSON serialization is attempting to deserialize an unexpected byte array.
    at System.Threading.Tasks.ValueTask`1.get_Result()
    at Telerik.Blazor.Components.FileSelect.Stream.FileInfoStream.<ReadBytesAsync>d__24.MoveNext()

Cause

The problem can occur when an Inversion of Control (IoC) container interferes with the SignalR hub operation. For example, we have received reports about Autofac:

caption Program.cs

builder.Host.UseServiceProviderFactory(new AutofacServiceProviderFactory());

The problem does not occur in FileSelect versions before 5.0.0, because the component used a slower legacy file management mechanism with string instead of byte[].

The following resources provide additional details:

• Technical description of the cause in the aspnetcore GitHub repository
• Closed issue in the aspnetcore GitHub repository
• Similar StackOverflow thread about the Blazor InputFile component.

Solution

To avoid the error, disable implicit parameters from services in the Blazor hub configuration:

caption Program.cs

builder.Services.AddHubOptions(options =>
{
    options.DisableImplicitFromServicesParameters = true;
});

See Also

• [FileSelect Overview]({%slug fileselect-overview%})