HTTP Error 404.13 - Not Found The request filtering module is configured to deny a request that exceeds the request content length.
Verify the configuration/system.webServer/security/requestFiltering/requestLimits@maxAllowedContentLength setting in the applicationhost.config or web.config file.
I've no idea to where can i config that, in asp.net core 2 there has change to use appsettings.json instead.
Even try to do this already, but it's not work.
services.Configure<FormOptions>(options =>
{
    options.MultipartBodyLengthLimit = 300_000_000;
});
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If you use IIS, you need add web.config in your asp.net core 2.0 app.
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <system.webServer>
    <security>
      <requestFiltering>
        <!-- This will handle requests up to 700MB (CD700) -->
        <requestLimits maxAllowedContentLength="737280000" />
      </requestFiltering>
    </security>
  </system.webServer>
</configuration>
If you are not using IIS you can use [RequestSizeLimit(long.MaxValue)] or [DisableRequestSizeLimit] attribute in your controller.
Also, you can add a global setting in Program.cs:
.UseKestrel(o => { o.Limits.MaxRequestBodySize = null; })