ASP.NET Core : Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead
You might have the following problem: https://github.com/aspnet/AspNetCore/issues/8302
And you can find more info here: https://github.com/aspnet/AspNetCore/issues/7644
A workaround until the issue is being solved is to allow Synchronous IO. Put this in Startup.cs for either Kestrel or IIS:
public void ConfigureServices(IServiceCollection services)
{
// If using Kestrel:
services.Configure<KestrelServerOptions>(options =>
{
options.AllowSynchronousIO = true;
});
// If using IIS:
services.Configure<IISServerOptions>(options =>
{
options.AllowSynchronousIO = true;
});
}
I had this issue with my unit tests. I had to update my TestServer to AlloSynchronousIO
Server = new TestServer(new WebHostBuilder().UseStartup<Startup>());
Server.AllowSynchronousIO = true;