We are receiving reports from multiple customers that they are unable to connect a Windows Store app to XAML Spy. Connection error 0x8007274C is shown, which indicates that the store app is unable to connect to the XAML Spy service hosted on the local machine.
In the past this error occurred when the project setting 'allow local network loopback' was unchecked. Checking the option, solved the issue. Now however, the error seems to occur even when the project setting is correctly set.
We do not know yet why this error occurs. We are currently investigating the cause of this issue, and will update this page when news is available.
Silverlight, Windows Phone and WPF apps seems to be unaffected.
It seems that the issue is related to having many Windows 8.1 AppContainers that are exempt from the local network traffic restriction. Resetting all loopback exemptions seems to solve the connection issue for XAML Spy.
Resetting loopback exemptions will disallow any app from connecting to the local machine. Visual Studio automatically re-enables the exemption when an app is launched from Visual Studio. If your app does require the loopback exemption, even without debugging, you'll need to exempt it manually with Fiddler.
Why the behavior occurs is still unknown, our investigation continues. We are looking into the behavior of the XAML designer in Visual Studio, it might be related. It does create many AppContainers named App.xxx that eventually cause XAML Spy to stop connecting.
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