new APIs for windows phone 8.1 - windows-phone-8

Question

I am trying to use these two methods (of WP 8) in windows phone 8.1, but it gives error and doesn't compile, most probably becasue they are removed. I tried searching the new APIs but couldn't get any. What are other alternatives for these.
Dispatcher.BeginInvoke( () => {}); msdn link
System.Threading.Thread.Sleep(); msdn link

Answer 1

They still exists for Windows Phone 8.1 SIlverlight Apps, but not for Windows Phone Store Apps. The replacements for Windows Store Apps is:
Sleep (see Thread.Sleep replacement in .NET for Windows Store):
await System.Threading.Tasks.Task.Delay(TimeSpan.FromSeconds(30));
Dispatcher (see How the Deployment.Current.Dispatcher.BeginInvoke work in windows store app?):
CoreDispatcher dispatcher = CoreWindow.GetForCurrentThread().Dispatcher;
await dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => { });

Answer 2

Dispatcher.BeginInvoke( () => {}); is replaced by
await this.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, async () => {});
and System.Threading.Thread.Sleep(); is replaced by
await Task.Delay(TimeSpan.FromSeconds(doubleValue));

Answer 3

Be aware that not only has the API changed (adopting the API from WindowsStore apps), but the way that the Dispatcher was obtained in windowsPhone 8.0 has changed as well.
#Johan Faulk's suggestion, although will work, may return null under a multitude of conditions.
Old code to grab the dispatcher:
var dispatcher = Deployment.Current.Dispatcher;
or
Deployment.Current.Dispatcher.BeginInvoke(()=>{
// any code to modify UI or UI bound elements goes here
});
New in Windows 8.1 Deployment is not an available object or namespace.
In order to make sure the Main UI Thread dispatcher is obtained, use the following:
var dispatcher = CoreApplication.MainView.CoreWindow.Dispatcher;
or
CoreApplication.MainWindow.CoreWindow.Dispatcher.RunAsync(
CoreDispatcherPriority.Normal,
()=>{
// UI code goes here
});
Additionally, although the method SAYS it will be executed Async the keyword await can not be used in the method invoked by RunAsync. (in the above example the method is anonymous).
In order to execute an awaitable method inside anonymous method above, decorate the anonymous method inside RunAsync() with the async keyword.
CoreApplication.MainWindow.CoreWindow.Dispatcher.RunAsync(
CoreDispatcherPriority.Normal,
**async**()=>{
// UI code goes here
var response = **await** LongRunningMethodAsync();
});

Answer 4

For Dispatcher, try this. MSDN
private async Task MyMethod()
{
await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () => { });
}
For Thread.Sleep() try await Task.Delay(1000). MSDN