c# - 避免竞争条件创建 StorageFolder

Question

我正在对一个新的 Win8 商店应用程序进行单元测试，并注意到我想避免的竞争条件。所以我正在寻找一种方法来避免这种竞争情况。

我有一个类，当实例化时调用一个方法以确保它有一个本地 StorageFolder。我的单元测试只是实例化对象并测试文件夹是否存在。有时文件夹不是，有时是，所以我认为这是一个竞争条件，因为 CreateFolderAsync 是异步的(很明显)。

public class Class1
{
    StorageFolder _localFolder = null;

    public Class1()
    {
        _localFolder = ApplicationData.Current.LocalFolder;
        _setUpStorageFolders();
    }

    public StorageFolder _LocalFolder
    {
        get
        {
            return _localFolder;
        }

    }


    async void _setUpStorageFolders()
    {
        try
        {
            _localFolder = await _localFolder.CreateFolderAsync("TestFolder", CreationCollisionOption.FailIfExists);

        }
        catch (Exception)
        {
            throw;
        }
    }
}

我的单元测试看起来像这样:

 [TestMethod]
    public void _LocalFolder_Test()
    {
        Class1 ke = new Class1();


        // TODO: Fix Race Condition 
        StorageFolder folder = ke._LocalFolder;

        string folderName = folder.Name;

        Assert.IsTrue(folderName == "TestFolder");

    }

Answer 1

正如 Iboshuizen 所建议的，我会同步执行此操作。这可以通过 async、task 和 await 来完成。有一个陷阱 - 无法在 Class1 的构造函数内完成设置，因为构造函数不支持异步/等待。因此 SetUpStorageFolders 现在是公开的，并且从测试方法中调用。

public class Class1
{
    StorageFolder _localFolder = null;

    public Class1()
    {
        _localFolder = ApplicationData.Current.LocalFolder;
                // call to setup removed here because constructors
                // do not support async/ await keywords
    }

    public StorageFolder _LocalFolder
    {
        get
        {
            return _localFolder;
        }

    }

      // now public... (note Task return type)
    async public Task SetUpStorageFolders()
    {
        try
        {
            _localFolder = await _localFolder.CreateFolderAsync("TestFolder", CreationCollisionOption.FailIfExists);

        }
        catch (Exception)
        {
            throw;
        }
    }
}

测试:

 // note the signature change here (async + Task)
 [TestMethod]
    async public Task _LocalFolder_Test()
    {
        Class1 ke = new Class1();
        // synchronous call to SetupStorageFolders - note the await
        await ke.SetUpStorageFolders();

        StorageFolder folder = ke._LocalFolder;

        string folderName = folder.Name;

        Assert.IsTrue(folderName == "TestFolder");
    }