![](/img/trans.png)
[英]Issue with Parameters.AddWithValue and looping through DataTable
[英]Issue looping through a DataTable Rows multiple times
::编辑::
好的,伙计们,看来我毕竟是个白痴。 这个问题与我的代码完全无关,而与Visual Studio有关的所有事情都与我的SQLite数据库用以前的(空的)版本覆盖了。 似乎确实有很多关于线程安全性的讨论,所以我将继续阅读更多内容!
::/编辑::
我试图使用多个后台工作程序一次遍历数据库100条记录的行,同时避免重复,但是我似乎遇到了一些问题。 基本上,我首先在一个循环中创建10个后台工作程序,然后将它们添加到列表中。 然后,我遍历List中的后台工作程序,并为每个工作程序执行RunWorkerAsync(),然后使主线程休眠5秒钟。 在每个后台工作程序的DoWork方法中,我让工作程序从数据库中选择100行,其中将特定字段设置为其默认值。 从这里开始,我想首先遍历返回的每一行,并将默认值更改为“ In Progress”值,然后再次遍历这些值,并实际进行所需的处理以找到这些字段的正确值。 我似乎遇到的问题是,在对结果进行第一次迭代后,我似乎有一个空的DataTable,并且我怀疑我的问题源自浅拷贝。 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);
}
}
}
}
有任何想法吗?
似乎您的延迟以及为什么要对其进行多线程处理,不是从数据库中读取记录,而是调用GeocodeServiceClient
。
您可以尝试重新设计main方法,以按顺序从数据库中获取所有记录并进行解析。 然后,您可以将该列表分为几部分,并启动后台工作人员以通过Geocode服务运行它们。
另一种选择是将记录放入队列中,并让每个后台工作人员从队列中弹出一个工作,然后在仍有未处理记录的情况下返回队列。 您将需要谨慎地锁定C#,使用Queue.Synchronized或lock()来保证线程安全会更好吗? 。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.