问题:

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.)

回答1:

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

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

回答2:

I suggest you use asynchronous lazy initialization.

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

You can then await it directly:

var rootFolder = await EnvironmentEx.AppRootFolder;

回答3:

use the await keyword

 public async static StorageFolder GetAppRootFolder()   {            return await ApplicationData                       .LocalFolder                       .CreateFolderAsync("folderName");  }

and in your code

var myRootFolder = await StaticClass.GetAppRootFolder(); // this is a synchronous call as we are calling await immediately and will return the StorageFolder.

回答4:

Here is an idea.

public Task Prop {     get     {         Func> f = async () =>          {              await Task.Delay(1000); return 0;          };         return f();     } }  private async void Test()  {     await this.Prop; }

but it creates a new Func object for every call this would do the same

public Task Prop {     get     {         return Task.Delay(1000).ContinueWith((task)=>0);     } }

You can't await a set since await a.Prop = 1; is not allowed

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