A method was called at an unexpected time

XSL picture XSL · Oct 27, 2012 · Viewed 19.5k times · Source

I'm trying to iterate all files in a directory using GetFilesAsync, but every time I call the GetResults method, it throws an exception that says

System.InvalidOperationException: A method was called at an unexpected time

The code is simply

var files = myStorageFolder.GetFilesAsync(); //runs fine
var results = files.GetResults(); //throws the exception

I'm new to Win 8 dev so I might be missing something obvious.

Edit (solved) I'm running my console application, but now that the program runs async, the files.GetResult() method no longer exists.

static void Main(string[] args)
{
   var files = GetFiles(myStorageFolder);
   var results = files.GetAwaiter().GetResults();//Need to add GetAwaiter()
}

static async Task GetFiles(StorageFolder sf)
{
   await sf.GetFilesAsync();
}

Answer

dcastro picture dcastro · Sep 21, 2013

If you don't want to use the asynckeyword (in my case, the code was inside a property, so asyncwasn't an option), you can use a TaskAwaiter instead, by chaining these two methods:

var folder = Package.Current.InstalledLocation.GetFolderAsync("folderName").GetAwaiter().GetResult();

This won't throw a InvalidOperationException nor cause a deadlock.