线程停止，XMLexception错误
线程停止，XMLexception错误
提问于 2014-02-25 00:23:35
因此，我启动了一个线程计时器，它可以工作，但线程计时器中的方法从yahoo API读取XML，有时对服务器的响应很差，因此抛出了XMLexception。但这似乎会停止线程，因为线程启动得很好，但当抛出异常时，所有线程都会停止。那么到底是怎么回事，我可以在每次另一个线程停止的时候启动一个线程吗？因为所有线程都会停止，然后再没有线程启动。
try
{
System.Threading.Timer timer;
timer = new System.Threading.Timer(new TimerCallback(TimerHelper), null, 0, 3000);
}
catch (Exception)
{
}TimerHelper(object obj)已尝试捕获异常。
public void TimerHelper(object obj)
{
try
{
if (dataGridView.Rows.Count > 0 && !(dataGridView.Rows[0].Cells[0].Value == null)) // Updates the rows idividualy as long as first row is not empty
{
string[] cells;
cells = new string[dataGridView.Columns.Count * dataGridView.Rows.Count];
for (int i = 0; i < dataGridView.RowCount; i++)
{
if (!(dataGridView.Rows[i].Cells[0].Value == null || dataGridView.Rows[i].Cells[0].Value.ToString() == "-")) // Makes sure that the row to update is not an empty row
{
String symbol;
symbol = Convert.ToString(dataGridView.Rows[i].Cells[0].Value);
String URLString2 = "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.quotes%20where%20symbol%20in%20(%22" + symbol + "%22)%0A%09%09&diagnostics=true&env=http%3A%2F%2Fdatatables.org%2Falltables.env";
for (int t = 2; t < dataGridView.Columns.Count; t++)
{
dataGridView.SuspendLayout();
XmlTextReader reader2 = new XmlTextReader(URLString2); // Makes the reader read from the string abow ( URL )
string NasdaqOpenTime = "09:00:00";
// if the market haven't been open for the day then theres no DaysLow value
if (dataGridView.Columns[t].HeaderText == "DaysLow" && DateTime.Now.CompareTo(DateTime.Parse(NasdaqOpenTime)) == -1)
{
cells[t - 2] = "0";
}
// if the market haven't been open for the day then theres no DaysHigh value
if (dataGridView.Columns[t].HeaderText == "DaysHigh" && DateTime.Now.CompareTo(DateTime.Parse(NasdaqOpenTime)) == -1)
{
cells[t - 2] = "0";
}
else
{
reader2.ReadToFollowing(dataGridView.Columns[t].HeaderText); // Reada until it fins the elemnt Bid , then stops on it
reader2.ReadStartElement(dataGridView.Columns[t].HeaderText); // Recognizes Bid as start element (Bid)
string temporary;
temporary = reader2.ReadString();
Trace.WriteLine(dataGridView.Columns[t].HeaderText + ": " + temporary);
cells[t - 2] = temporary; // Reads the text in between (Declared as a string) actualy the bid value
reader2.ReadEndElement(); // Checks that the current nod is an end element (/Bid) if so then continue
reader2.ResetState();
}
}
}
}
for (int h = 0; h < dataGridView.Rows.Count; h++)
{
for (int t = 2; t < dataGridView.Columns.Count; t++)
{
dataGridView.Rows[h].Cells[t].Value = cells[t - 2];
}
}
}
}
catch (XmlException)
{
}
catch (Exception)
{
}
}下面是在TimerHelper(object obj)中跟踪的值的输出示例。
'FetchBySymbol.vshost.exe' (Managed (v4.0.30319)): Loaded 'C:\Users\Mattias\documents\visual studio 2012\Projects\FetchBySymbol\FetchBySymbol\bin\Debug\FetchBySymbol.exe', Symbols loaded.
'FetchBySymbol.vshost.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Configuration\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Configuration.dll'
Ask: 37.44
Bid: 37.43
...
...
...
Ask: 37.44
Bid: 37.43
Ask: 37.42
Bid: 37.41
The thread '<No Name>' (0x104c) has exited with code 0 (0x0).
The thread '<No Name>' (0x1920) has exited with code 0 (0x0).
A first chance exception of type 'System.Net.WebException' occurred in System.dll
A first chance exception of type 'System.Net.WebException' occurred in System.Xml.dll
The thread '<No Name>' (0xe3c) has exited with code 0 (0x0).
The thread '<No Name>' (0x1af0) has exited with code 0 (0x0).
The thread '<No Name>' (0x1b18) has exited with code 0 (0x0).
The thread '<No Name>' (0xb90) has exited with code 0 (0x0).
The thread '<No Name>' (0x20) has exited with code 0 (0x0).为什么它会退出？
回答 2
Stack Overflow用户
发布于 2014-02-25 01:13:06
不要捕获泛型Exception，因为使用(来自您的帖子的代码)
catch (Exception) { }可能导致每个可能的Exception从您的手指间溜走的情况。
试着找出System.Net.WebException可能发生的地方，并命名你的线程，这样你就可以更深入地了解正在发生的事情，例如：
(new Thread(() => {}) { Name = "Some thread" }).Start();输出
The thread 'Some thread' (0x260c) has exited with code 0 (0x0).如果你想知道这些first chance exceptions是什么，请看这里http://blogs.msdn.com/b/davidklinems/archive/2005/07/12/438061.aspx
正如@BlackICE所说，请发布丢失的代码片段，以便解决您的问题。
编辑：
你确定你正在寻找正确的地方来解决这个问题吗？如前所述，线程退出不是问题的征兆(您确实希望线程在完成工作后退出)，也不是第一次机会异常(抛出异常但已处理)。
这会不会是CGd计时器的问题，就像这篇文章所说的那样？
System.Threading.Timer not firing after some time
编辑：
试试这样的东西，好吗？它将永远以非阻塞的方式运行。只需添加一些更详细的异常处理;)。
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = this;
Task.Factory.StartNew(() => DoTheMagic());
}
// Here the magic occurs
public async Task DoTheMagic()
{
while (true)
{
string url = "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.quotes%20where%20symbol%20in%20(%22YHOO%22)&diagnostics=true&env=http://datatables.org/alltables.env";
string raw = await GetResponse(url);
var parsed = await ParseXml(raw);
// Pass results to UI
Dispatcher.BeginInvoke(new Action(() =>
{
if (parsed == null || !parsed.Any())
return;
var now = DateTime.Now;
foreach (var tuple in parsed)
textBox.Text += string.Format("{0} {1} = {2}{3}", now, tuple.Item1, tuple.Item2, Environment.NewLine);
}));
Thread.Sleep(3000);
}
}
// Get response from service
public async Task<string> GetResponse(string url)
{
string content = null;
try
{
var request = WebRequest.Create(url);
var response = await request.GetResponseAsync();
var stream = response.GetResponseStream();
if (stream == null)
return null;
using (var reader = new StreamReader(stream, Encoding.GetEncoding("utf-8")))
content = await reader.ReadToEndAsync();
}
catch
{
System.Diagnostics.Debug.WriteLine("ZOMG!");
}
return content;
}
// Parse response with your logic
public Task<List<Tuple<string, string>>> ParseXml(string xml)
{
return Task.Factory.StartNew(() =>
{
try
{
var nodes = new string[] { "Symbol", "Ask", "Bid" };
var result = new List<Tuple<string, string>>();
using (var reader = new XmlTextReader(new StringReader(xml)))
{
reader.MoveToContent();
while (reader.Read())
{
if (reader.NodeType.Equals(XmlNodeType.Element))
{
if (nodes.Contains(reader.LocalName))
result.Add(new Tuple<string, string>(reader.LocalName, reader.ReadElementContentAsString()));
}
}
}
return result;
}
catch
{
System.Diagnostics.Debug.WriteLine("I haz exception!!1");
return null;
}
});
}
}输出
Stack Overflow用户
发布于 2014-02-25 02:00:09
线程退出是正常的，看看退出代码：
The thread '<No Name>' (0xe3c) has exited with code 0 (0x0).
这将在每次计时器触发时发生，并且从您的输出看，计时器是周期性地触发的(您会得到多个线程退出，显然是周期性的)。您可能希望在异常处理程序中放置一些东西，而不是只吃它们，然后您可以设置断点，并查看为什么对计时器处理程序的后续调用无法运行您的代码。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/21993242
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