Create sub folders in My Pictures from Windows Sto

问题:

I'm trying to create a folder structure within My Pictures folder from a Windows store app. But I can't seem to get pass the first level.

I create my first level folder using the following code:

IAsyncOperation<StorageFolder> appFolder = Windows.Storage.KnownFolders.PicturesLibrary.GetFolderAsync("AppPhotos");

if (appFolder==null)
{
    //Create folder
    appFolder = Windows.Storage.KnownFolders.PicturesLibrary.CreateFolderAsync("AppPhotos");
}

Now I want to create another folder below this call Level1.

I was expecting to be able to do the following:

appFolder.CreateFolderAsync("Level1");

But I don't have a CreateFolderAsync method from my appFolder.

So, how can I create that Folder and then how would I then select it?

Thanks in advance

I'm using Visual Studio 2012, C#4.5, XAML and I'm writing a windows store app.

回答1:

You seem to have missed the async/await revolution there and assume the operation to get a folder is a folder. This should work:

var appFolder = await Windows.Storage.KnownFolders.PicturesLibrary.GetFolderAsync("AppPhotos");

if (appFolder == null)
{
    //Create folder
    appFolder = await Windows.Storage.KnownFolders.PicturesLibrary.CreateFolderAsync("AppPhotos");
}

You also need to add the async keyword in the method signature wherever the above code is located and then also if your method returns a value of type T - change it to return Task<T>, so for method signature:

private void MyMethod()

you would change it to

private async Task MyMethod()

and if your current signature is

private bool MyMethod()

you would need to do

private async Task<bool> MyMethod()

Finally in that last case - you would need to also change your calls from

var myValue = MyMethod();

to

var myValue = await MyMethod();

etc. marking all methods that make calls that await other methods with the async keyword.

回答2:

To create a folder and a subFolder in picture library:

  StorageFolder appFolder;
  try
    {
       appFolder = await  Windows.Storage.KnownFolders.PicturesLibrary.GetFolderAsync("AppPhotos");

    }
  catch (Exception ex)
    {

      appFolder = null;

     }
 if (appFolder == null)
   {

   //Create folder
    appFolder = await Windows.Storage.KnownFolders.PicturesLibrary.CreateFolderAsync("AppPhotos");

    }

    //Create sub-folder
   await appFolder.CreateFolderAsync("level1");