Question

我想设计一个Windows表单应用程序，在数组中包含我的数据（大约70k值），以便在最短的时间内将其传输到csv文件，csv文件路径和名称由windows表单应用程序提供。

仅当按下名为start的第一个按钮时才会进行数据传输，并且无论值的数量如何，都会在按下第二个按钮时停止数据传输。

以下是代码：

public static void Write(double[] data, string outputPath)
{ 
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < data.GetLength(0); i++)
    {
        sb.AppendLine(string.Join(",", data[i]));
    }
    File.WriteAllText(outputPath, sb.ToString());
}

这是我正在使用的函数，其中包含varibale dscaledData，它是一个数组。我想从这个数组中获取值并将其存储在csv文件中

Write(dScaledData, @csvadd);

@ part显示带有名称的csv路径存储在dscaledData变量中的数据值非常大。 70K

Answer 1

You want to use the stop button to somehow break your write loop. But as it is, it will keep running and indeed block the ui thread. So you need to run the write loop in a different thread..

There are various way to do it in .NET, e.g. a Task.Factory, threads or a BackgroundWorker.

Here is a simple but effective implementation using a Task.Factory:

We create a class level variable stopped which we set and reset from the Buttons. There are other, more involved ways to cancel a Task, see here, but this is good enough for the purpose..

For my tests I also create dummy data..

private void cb_Stop_Click(object sender, EventArgs e)
{  stopped = true;   // this will be checked in our output loop   }

private void cb_Start_Click(object sender, EventArgs e)
{
    stopped = false;
    // create my test data..
    List<double> data = new List<double>();
    for (int i = 0; i < 10000000; i++) data.Add((i+ 1d) / i * 1d );
    string filename = "D:\\xxxxx.txt";

    // this is an optional callback to provide feedback. 
    // It obviuosly slows things down greatly..
    Action<int> callback = (value) => st_lines.Invoke(new Action(() 
                         => st_lines.Text = value + " lines written.."));
    // now we start the write loop in another task..
    // ..passing in our data and (optinally) the callback
    Task myFirstTask = Task.Factory.StartNew(() 
                     => Write(data.ToArray(), filename, callback));
}

static bool stopped = true;   // our flag

public static void Write(double[] data, string outputPath, Action<int> aCallback)
{    // your write loop
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < data.GetLength(0); i++)
    {
        if (stopped) break;   // our new test
        sb.AppendLine(string.Join(",", data[i]));
        aCallback( i );       // optional callback
    }
    File.WriteAllText(outputPath, sb.ToString());
}

A few notes about the timing situation:

Adding 70k lines to a StringBuilder should not take a lot of time. Look at my code: I had to crank the test data up to 10M lines to even be able to press the stop button on my machine!

Maybe the creation of the data is the bottleneck or maybe it is the writing to disk..? Or maybe there is no bottleneck?? You should understand this before you decide on an implementation!

If other parts are identified as the bottlenaeck you would have to change the code accordingly to break out of the other loops..

I have added the callback mechanism so you can see how you can bring information about the progress of the task back to the UI thread. It should help your users decide on whether stopping the task makes sense..

But adding the callback slows things down a lot, so instead of calling it for every single line you could do it like this: if (i % 1000 == 0 ) aCallback(i); and only update the progress label (or a ProgressBar, of course) every 1000 lines.

Answer 2

You will want to use the BackgroundWorker for this. It is exactly what you Need.

Do not use File.WriteAllText, but use File.WriteLine in the worker-thread.

In my opinion 70k lines is not very much and if your amount of data doesnt grow substantially in the future, a human will not be able to start/stop unless you artificially pause the writer thread with a Thread.Sleep()

如何创建由Start-and-Buttons控制的CSV文件

2 个答案: