Asynchronous C# component

Question

Hi all, I am doing a simple C# component. In component, I will create a folder, after create successfully, I will return a string to notify. But the problem is I can't notify when it complete. I can create a folder but always notify before it complete. I post my code below. private async Task createNewCaching(string productId) { mFolder = await KnownFolders.PicturesLibrary.CreateFolderAsync(productId,CreationCollisionOption.OpenIfExists); } public String getFolderPath(string productId) { //createNewCaching(productId); Task t = createNewCaching(productId); while (mFolder == null) Thread.Sleep(1000); if (mFolder != null) return mFolder.Path.ToString(); else return "not created"; }

Answer 1

Sorry, I re-post my code.

private async Task createNewCaching(string productId) 
{
  mFolder = await KnownFolders.PicturesLibrary.CreateFolderAsync(productId, CreationCollisionOption.OpenIfExists);
}

public String getFolderPath(string productId)
{ 
  //createNewCaching(productId); 
  Task t = createNewCaching(productId); 
  if (mFolder != null) 
  return mFolder.Path.ToString(); 
  else 
  return "not created"; 
}

Answer 2

Design your method as below:

 

        StorageFolder mFolder;
        private async Task<StorageFolder> createNewCaching(string productId)
        {
            return await KnownFolders.PicturesLibrary.CreateFolderAsync(productId, CreationCollisionOption.OpenIfExists);
        }

        public async Task<String> getFolderPath(string productId)
        {
            mFolder = await createNewCaching(productId);
            if (mFolder != null)
                return mFolder.Path.ToString();
            else
                return "not created";
        }

 And call it via the await key word.

 

var result = await getFolderPath(...);

 

---

Bob Bao [MSFT]
MSDN Community Support | Feedback to us

Answer 3

Hi Bob,

I think it's not correct solution. I want to call function getFolderPath from javascript. But if you design like this, we cannot pass result to javascript. My idea is C# component do asynchronous function, and notify to javascript when complete. Is it possible? And how to do?

Thanks,

Vivian

Answer 4

Vivian, why do you want to write a C# WinMD object to do this?  Why don't you keep all of your code javascript?

-Jeff

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Jeff Sanders (MSFT)

Answer 5

Vivian,

I outlined how to write a C# component and call async methods on it here:

http://social.msdn.microsoft.com/Forums/en-US/winappswithhtml5/thread/a038defe-2594-4c1a-85ef-7a98a0a409b2/

Is this similar to what you are trying to do?

-Jeff

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Jeff Sanders (MSFT)

Answer 6

Hi Jeft,

I will try it in my case.

Thanks,

Vivian

Answer 7

Hi Jeft,

I am confusing with 2 solutions. The first solution I will do all in javascript, but it seems to be loose control when the program have a lot of downloads and cache functions. So I try the second solutions, using C# to do everything about cache and download, after that provide data to javascript.

Vivian

Answer 8

As jpsanders said, please refer to the link he provided. You could modify your C# as below, to create a WinRT class that can be invoked in JS:

    public sealed class Helper
    {
        static StorageFolder mFolder;
        private static async Task<StorageFolder> createNewCaching(string productId)
        {
            return await KnownFolders.PicturesLibrary.CreateFolderAsync(productId, CreationCollisionOption.OpenIfExists);
        }

        private static async Task<String> getFolderPath(string productId)
        {
            mFolder = await createNewCaching(productId);
            if (mFolder != null)
                return mFolder.Path.ToString();
            else
                return "not created";
        }

        public IAsyncOperation<string> GetFolderPath(string productID)
        {
            return AsyncInfoFactory.Create(() => getFolderPath(productID));
        }
    }

and invoke in JS:

            (new NameSpace.Helper).getFolderPath("abc").then(

                function (p) {

                var result = p;

                }

            );

---

Bob Bao [MSFT]
MSDN Community Support | Feedback to us

Answer 9

Hi Jeft and Bob,

It work now. Thank you very much.

Vivian