:: EDIT ::
好的伙计们，看来我毕竟是个白痴。这个问题与我的代码没有任何关系，而且与Visual Studio一起使用以前的（和空的）版本覆盖了我的SQLite数据库。似乎对线程安全进行了很好的讨论，所以我会继续阅读更多内容！
:: / EDIT ::
我试图使用多个后台工作程序一次循环数据库的100行记录，同时避免重复，但我似乎遇到了一些问题。 基本上，我首先在循环中创建10个后台工作程序，然后将它们添加到List中。然后我循环遍历List中的后台工作程序，并为每个我执行RunWorkerAsync（），然后将主线程休眠5秒。在每个后台工作程序的DoWork方法中，我让worker从数据库中选择100行，其中特定字段设置为其默认值。 从这里开始，我想首先循环遍历每个返回的行并将该默认值更改为“In Progress”值，然后再次遍历这些值并实际执行为这些字段查找正确值所需的处理。我似乎遇到的问题是，在第一次迭代结果后，我似乎有一个空的DataTable，我怀疑我的问题源于浅层复制。 这是代码：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.IO;
using System.Text;
using DBFill.GeoCodeService;
using System.Diagnostics;
using System.Runtime.Serialization.Formatters.Binary;
namespace DBFill {
class Program {
public static int completedGeocodes = 0;
static void Main(string[] args) {
SQLiteDatabase db = new SQLiteDatabase("zipCodes.s3db");
List<BackgroundWorker> workers = new List<BackgroundWorker>();
for (int i = 0; i < 10; i++) {
BackgroundWorker b = new BackgroundWorker();
b.DoWork += new DoWorkEventHandler(worker_DoWork);
b.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
b.WorkerReportsProgress = true;
b.ProgressChanged += new ProgressChangedEventHandler(b_ProgressChanged);
workers.Add(b);
}
int counter = 0;
foreach (BackgroundWorker b in workers) {
Debug.WriteLine("Worker {0} is starting.", counter);
b.RunWorkerAsync(b);
counter++;
System.Threading.Thread.Sleep(5000);
}
Boolean running = true;
while (running) {
running = false;
foreach (BackgroundWorker b in workers) {
Debug.WriteLine("Checking background Worker");
if (b.IsBusy) {
running = true;
}
}
System.Threading.Thread.Sleep(5000);
}
}
static void b_ProgressChanged(object sender, ProgressChangedEventArgs e) {
Console.WriteLine(".");
}
static void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
}
static void worker_DoWork(object sender, DoWorkEventArgs e) {
BackgroundWorker b = (BackgroundWorker)e.Argument;
SQLiteDatabase db = new SQLiteDatabase("zipCodes.s3db");
DataTable results = get100Records();
DataTable temp = DeepClone<DataTable>(results);//results;
Dictionary<String, String> marker = new Dictionary<string, string>();
marker["LATITUDE"] = "In Progress";
foreach (DataRow row in temp.Rows) {
Debug.WriteLine("Working with zip {0}", row["ZIP_CODE"]);
db.Update("ZIP_CODES", marker, String.Format("ZIP_CODE = '{0}'", row["ZIP_CODE"]));
}
foreach (DataRow row in results.Rows) {
String geoCodeResponse = GeoCodeZip(row["ZIP_CODE"].ToString());
Debug.WriteLine(String.Format("Attempting Zip: {0}", row["ZIP_CODE"].ToString()));
if (geoCodeResponse != "There was an error") {
marker["LATITUDE"] = geoCodeResponse.Split(',')[0];
marker["LONGITUDE"] = geoCodeResponse.Split(',')[1];
Console.WriteLine(String.Format("#{0} updated successfully", completedGeocodes));
}
else {
marker["LATITUDE"] = "Not Set";
Console.WriteLine(String.Format("#{0} failed", completedGeocodes));
}
db.Update("ZIP_CODES", marker, String.Format("ZIP_CODE = '{0}'", row["ZIP_CODE"]));
db.ExecuteNonQuery("commit");
b.ReportProgress(1);
completedGeocodes++;
}
}
private static DataTable get100Records() {
SQLiteDatabase db = new SQLiteDatabase("zipCodes.s3db");
DataTable results = db.GetDataTable("select ZIP_CODE from ZIP_CODES where LATITUDE = 'Not Set' LIMIT 100");
return results;
}
private static String GeoCodeZip(String zip) {
try {
GeocodeRequest request = new GeocodeRequest();
request.Credentials = new GeoCodeService.Credentials();
request.Credentials.ApplicationId = "API_KEY";
request.Query = zip;
ConfidenceFilter[] filters = new ConfidenceFilter[1];
filters[0] = new ConfidenceFilter();
filters[0].MinimumConfidence = Confidence.High;
GeocodeOptions opts = new GeocodeOptions();
opts.Filters = filters;
request.Options = opts;
GeocodeServiceClient service = new GeocodeServiceClient("BasicHttpBinding_IGeocodeService");
GeocodeResponse response = service.Geocode(request);
if (response.Results.Length > 0) {
return String.Format("{0},{1}", response.Results[0].Locations[0].Latitude, response.Results[0].Locations[0].Longitude);
}
else {
Debug.WriteLine(String.Format("{0}", response.ResponseSummary.FaultReason));
return "There was an error";
}
}
catch (Exception e) {
Debug.WriteLine(e.Message);
return "There was an error";
}
}
public static T DeepClone<T>(T obj) {
using (var ms = new MemoryStream()) {
var formatter = new BinaryFormatter();
formatter.Serialize(ms, obj);
ms.Position = 0;
return (T)formatter.Deserialize(ms);
}
}
}
}
任何想法？
答案 0 :(得分：1)
似乎您的延迟以及为什么要多线程化它，不是要从数据库中读取记录，而是要调用GeocodeServiceClient。
您可以尝试重新编写main方法，按顺序从DB中获取所有记录并解析它们。然后，您将该列表拆分为偶数块并启动后台工作程序以通过地理编码服务运行它们。
另一种选择是将记录放入队列中，让每个后台工作者从队列中弹出一个后台工作，然后在仍有未处理的记录时返回队列。您需要小心锁定In C# would it be better to use Queue.Synchronized or lock() for thread safety?。