我试图使用文件IO操作实现读写操作，并将这些操作封装到其中TransformBlock，以使这些操作线程安全，而不是使用锁定机制。
但是问题是，当我尝试并行写入5个文件时，内存异常，使用此实现会阻塞UI线程。该实现在Windows Phone项目中完成。请指出此实现中的错误。
文件IO操作
public static readonly IsolatedStorageFile _isolatedStore = IsolatedStorageFile.GetUserStoreForApplication();
public static readonly FileIO _file = new FileIO();
public static readonly ConcurrentExclusiveSchedulerPair taskSchedulerPair = new ConcurrentExclusiveSchedulerPair();
public static readonly ExecutionDataflowBlockOptions exclusiveExecutionDataFlow
= new ExecutionDataflowBlockOptions
{
TaskScheduler = taskSchedulerPair.ExclusiveScheduler,
BoundedCapacity = 1
};
public static readonly ExecutionDataflowBlockOptions concurrentExecutionDataFlow
= new ExecutionDataflowBlockOptions
{
TaskScheduler = taskSchedulerPair.ConcurrentScheduler,
BoundedCapacity = 1
};
public static async Task<T> LoadAsync<T>(string fileName)
{
T result = default(T);
var transBlock = new TransformBlock<string, T>
(async fName =>
{
return await LoadData<T>(fName);
}, concurrentExecutionDataFlow);
transBlock.Post(fileName);
result = await transBlock.ReceiveAsync();
return result;
}
public static async Task SaveAsync<T>(T obj, string fileName)
{
var transBlock = new TransformBlock<Tuple<T, string>, Task>
(async tupleData =>
{
await SaveData(tupleData.Item1, tupleData.Item2);
}, exclusiveExecutionDataFlow);
transBlock.Post(new Tuple<T, string>(obj, fileName));
await transBlock.ReceiveAsync();
}
MainPage.xaml.cs用法
private static string data = "vjdsskjfhkjsdhvnvndjfhjvkhdfjkgd"
private static string fileName = string.Empty;
private List<string> DataLstSample = new List<string>();
private ObservableCollection<string> TestResults = new ObservableCollection<string>();
private static string data1 = "hjhkjhkhkjhjkhkhkjhkjhkhjkhjkh";
List<Task> allTsk = new List<Task>();
private Random rand = new Random();
private string fileNameRand
{
get
{
return rand.Next(100).ToString();
}
}
public MainPage()
{
InitializeComponent();
for (int i = 0; i < 5; i ++)
{
DataLstSample.Add((i % 2) == 0 ? data : data1);
}
}
private void Button_Click(object sender, RoutedEventArgs e)
{
AppIsolatedStore_TestInMultiThread_LstResultShouldBeEqual();
}
public async void AppIsolatedStore_TestInMultiThread_LstResultShouldBeEqual()
{
TstRst.Text = "InProgress..";
allTsk.Clear();
foreach(var data in DataLstSample)
{
var fName = fileNameRand;
var t = Task.Run(async () =>
{
await AppIsolatedStore.SaveAsync<string>(data, fName);
});
TestResults.Add(string.Format("Writing file name: {0}, data: {1}", fName, data));
allTsk.Add(t);
}
await Task.WhenAll(allTsk);
TstRst.Text = "Completed..";
}
保存和加载异步数据
/// <summary>
/// Load object from file
/// </summary>
private static async Task<T> LoadData<T>(string fileName)
{
T result = default(T);
try
{
if (!string.IsNullOrWhiteSpace(fileName))
{
using (var file = new IsolatedStorageFileStream(fileName, FileMode.OpenOrCreate, _isolatedStore))
{
var data = await _file.ReadTextAsync(file);
if (!string.IsNullOrWhiteSpace(data))
{
result = JsonConvert.DeserializeObject<T>(data);
}
}
}
}
catch (Exception ex)
{
//todo: log the megatron exception in a file
Debug.WriteLine("AppIsolatedStore: LoadAsync : An error occured while loading data : {0}", ex.Message);
}
finally
{
}
return result;
}
/// <summary>
/// Save object from file
/// </summary>
private static async Task SaveData<T>(T obj, string fileName)
{
try
{
if (obj != null && !string.IsNullOrWhiteSpace(fileName))
{
//Serialize object with JSON or XML serializer
string storageString = JsonConvert.SerializeObject(obj);
if (!string.IsNullOrWhiteSpace(storageString))
{
//Write content to file
await _file.WriteTextAsync(new IsolatedStorageFileStream(fileName, FileMode.Create, _isolatedStore), storageString);
}
}
}
catch (Exception ex)
{
//todo: log the megatron exception in a file
Debug.WriteLine("AppIsolatedStore: SaveAsync : An error occured while saving the data : {0}", ex.Message);
}
finally
{
}
}
编辑：
它具有内存异常的原因是由于我拿走的数据字符串太大的一个原因。字符串是链接：http : //1drv.ms/1QWSAsc
但是第二个问题是，如果我也添加少量数据，那么它将阻塞UI线程。代码在UI上执行任何任务吗？
不，您使用的并发对使用默认线程池执行任务，并使用Runmethod实例化任务，因此问题不在这里。但是这里的代码有两个主要威胁：
var transBlock = new TransformBlock<string, T>
(async fName =>
{
// process file here
}, concurrentExecutionDataFlow);
您确实不应该transBlock每次都创建。其主要思想TPL Dataflow是创建一次块，然后再使用它们。因此，您应该将应用程序重构为减少实例化的块数，否则就不TPL Dataflow应该使用这种情况。
代码中的另一个威胁是您将显式阻塞线程！
// Right here
await Task.WhenAll(allTsk);
TstRst.Text = "Completed..";
从同步事件处理程序中await的async void方法中调用for任务会阻塞线程，因为默认情况下它将捕获同步上下文。首先，async void应避免。其次，如果您是异步的，则应该一直保持异步，因此事件处理程序也应该是异步的。第三，您可以对您的任务使用延续来更新UI或使用当前同步上下文。
因此，您的代码应如下所示：
// store the sync context in the field of your form
SynchronizationContext syncContext = SynchronizationContext.Current;
// avoid the async void :)
public async Task AppIsolatedStore_TestInMultiThread_LstResultShouldBeEqual()
// make event handler async - this is the only exception for the async void use rule from above
private async void Button_Click(object sender, RoutedEventArgs e)
// asynchronically wait the result without capturing the context
await Task.WhenAll(allTsk).ContinueWith(
t => {
// you can move out this logic to main method
syncContext.Post(new SendOrPostCallback(o =>
{
TstRst.Text = "Completed..";
}));
}
);
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