about LegacyAspNetSynchronizationContext and async

Question

User-507696518 posted

public async Task<ActionResult> TestModelBinder(CancellationToken cancellationToken)
        {
           
            await Task.Delay(1);
            var x = System.Web.HttpContext.Current;
            return Content("test");

        }

this is one of action in my controller,and when the SynchronizationContext.Current type is

LegacyAspNetSynchronizationContext,the variable x will be null!but when

the SynchronizationContext.Current type is AspNetSynchronizationContext,the variable x will

not be null. I want to know what is the cause of it.thanks.

Answer 1

User-707554951 posted

Hi huangke1993,

The legacy type (LegacyAspNetSynchronizationContext) in your call stack indicates that your web.config settings are incorrect. Set targetFramework to 4.5 or higher.

async cause undefined behavior on earlier versions of ASP.NET. 

Related thread:

https://stackoverflow.com/a/38119187

Best regards 

Cathy

Answer 2

User-507696518 posted

thank you