.Net Core 3 preview: Synchronous operations are disallowed

.net core preview synchronous
Norbert Norbertson picture Norbert Norbertson · Mar 7, 2019 · Viewed 8.7k times · Source

I have an AngularJs app that I am porting to .Net Core.

It was working fine in the previous version of .Net Core 3 preview; 3.2.

However, after upgrading to latest 3.3 some of the get requests are returning this error:

InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.

I can't see why this is happening with only some requests and not others.

I believe that by default AngularJs does async: xhr.open(method, url, true);

Can anyone shed some light on this?

Answer

Norbert Norbertson picture Norbert Norbertson · Mar 8, 2019

This problem is described here: https://github.com/aspnet/AspNetCore/issues/8302

The workaround for now is to manually set AllowSynchronous to true in startup.cs;

// Startup.ConfigureServices

services.Configure<IISServerOptions>(options =>
{
  options.AllowSynchronousIO = true;
});

thanks to Chris Ross for the help

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