Async property in c#

Question

In my windows 8 application there is a global class where there are a few static properties like:

public class EnvironmentEx
{
     public static User CurrentUser { get; set; }
     //and some other static properties

     //notice this one
     public static StorageFolder AppRootFolder
     {
         get
         {
              return KnownFolders.DocumentsLibrary                    
               .CreateFolderAsync("theApp", CreationCollisionOption.OpenIfExists)
               .GetResults();
         }
     }
}

You can see I want to use the application root folder somewhere else in the project, so I make it a static property. Inside the getter, I need to make sure the root folder exists,otherwise create it. But the CreateFolderAsync is an async method, here I need a synchronized operation. I tried GetResults() but it throws an InvalidOperationException. What is the correct implementation? (The package.appmanifest is correctly configured, the folder is actually created.)

Answer 1

I suggest you use asynchronous lazy initialization.

public static readonly AsyncLazy<StorageFolder> AppRootFolder =
    new AsyncLazy<StorageFolder>(() =>
    {
      return KnownFolders.DocumentsLibrary                    
          .CreateFolderAsync("theApp", CreationCollisionOption.OpenIfExists)
          .AsTask();
    });

You can then await it directly:

var rootFolder = await EnvironmentEx.AppRootFolder;

Answer 2

Good solution: Don't make a property. Make an async method.

"I hate await, how can I make everything synchronous?" solution: How to call asynchronous method from synchronous method in C#?