The goal of the function is to fill the from (from 3rd party website) and click the submit button and gets the html source of the submitted result page. This task needs to be done on click event of the button in asp.net. If the function returns true, do some sql tasks at the end. I read about the Asynchronous Handler in asp.net but really beginner of that and not sure what a best solution is to simulate this type of task in asp.net.
Protected Sub lbtnSave_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles lbtnSave.Click
If CrawlWebSite() then
'Save
End If
End Sub
Private Function CrawlWebSite() As Boolean
Dim objBrowser = CreateObject("InternetExplorer.Application")
Dim url As String = "https://test.com/Search.do?subAction=reset&searchType=ind"
With objBrowser
.navigate(url)
System.Threading.Thread.Sleep(1000)
Dim StartTime As DateTime
Dim ElapsedTime As TimeSpan
Dim bLong As Boolean = False
StartTime = Now
Do While .busy = True
ElapsedTime = Now().Subtract(StartTime)
If (ElapsedTime.TotalSeconds Mod 60) >= 55 Then
bLong = True
Exit Do
End If
System.Threading.Thread.Sleep(1000)
开发者_StackOverflow社区 Loop
If bLong = True Then
PageName.Alert(Page, "There is a delay retrieving the website for checking NPI. Please try again.")
Return False
End If
.document.getElementById("lastname").Value = txtLastName.Text.Trim
.document.getElementById("searchNpi").Value = txtUPIN.Text.Trim
.document.getElementsByTagName("input").item(7).click()
System.Threading.Thread.Sleep(1000)
bLong = False
StartTime = Now
Do While .busy = True
'There is a delay retrieving the website. Continue ?
ElapsedTime = Now().Subtract(StartTime)
If (ElapsedTime.TotalSeconds Mod 60) >= 50 Then
bLong = True
Exit Do
End If
System.Threading.Thread.Sleep(1000)
Loop
If bLong = True Then
PageName.Alert(Page, "There is a delay retrieving the website. Please try again.")
Return False
End If
If .document.getElementById("lastname") Is Nothing Then
'We have result
Return True
Else
PageName.Alert(Page, "Attention: No matching records found.")
Return False
End If
End With
End Function
Here are some classes used in implementing long-polling using HttpHandlers. I use this solution for operations that take a LONG time to finish. There are basically 6 classes (see below). Some of these classes may end-up being unneeded for YOUR purposes, but they made sense for mine. These have "mostly" been sanitized for you.
- Controller: Processes actions required to create a valid response (db operations etc.)
- Processor: Manages asynch communication with the web page (itself)
- IAsynchProcessor: The service processes instances that implement this interface
- Sevice: Processes request objects that implement IAsynchProcessor
- Request: The IAsynchProcessor wrapper containing your response (object)
- Response: Contains custom objects or fields
If you need help with the JavaScript or HTML add-in a comment below...I will write something for you.
HTTP HANDLERS:
using System;
using System.Configuration;
using System.Web;
using System.Web.Script.Serialization;
using System.Web.Services;
using System.Web.SessionState;
namespace Concept.LongPolling.Handlers
{
/// <summary>
/// Summary description for Controller
/// </summary>
public class Controller : IHttpHandler, IReadOnlySessionState
{
#region CONSTRUCTORS
#endregion
#region PROPERTIES
/// <summary>Gets a Boolean value indicating that another request can use the current instance of the DefaultHttpHandler class.</summary>
/// <remarks>Returning true makes the same AsyncHttpHandler object be used for all requests.</remarks>
/// <remarks>Returning false here makes ASP.Net create object per request.</remarks>
public bool IsReusable { get { return true; } }
#endregion
#region METHODS
/// <summary>Enables synchronous processing of HTTP Web requests</summary>
/// <param name="context">An HttpContext object that provides references to the intrinsic server objects</param>
/// /// <remarks>This is where you would send commands to the controller that would affect processing in some manner.</remarks>
public void ProcessRequest(HttpContext context)
{
throw new NotImplementedException();
}
/// <summary>Creates the response object which is serialized back to the client</summary>
/// <param name="response"></param>
public static Response CreateResponse(Response response)
{
try
{
response.Generate();
}
catch (System.Exception ex)
{
response.SessionValid = false;
}
return response;
}
#endregion
}
}
using System;
using System.Configuration;
using System.Web;
using System.Web.Script.Serialization;
using System.Web.Services;
using System.Web.SessionState;
using Concept.LongPolling.LongPolling;
namespace Concept.LongPolling.Handlers
{
/// <summary>
/// Summary description for Processor
/// </summary>
public class Processor : IHttpHandler, IHttpAsyncHandler, IReadOnlySessionState
{
#region CONSTRUCTORS
#endregion
#region PROPERTIES
/// <summary>Gets a Boolean value indicating that another request can use the current instance of the DefaultHttpHandler class.</summary>
/// <remarks>Returning true makes the same AsyncHttpHandler object be used for all requests.</remarks>
/// <remarks>Returning false here makes ASP.Net create object per request.</remarks>
public bool IsReusable { get { return false; } }
#endregion
#region METHODS
/// <summary>Enables synchronous processing of HTTP Web requests</summary>
/// <param name="context">An HttpContext object that provides references to the intrinsic server objects</param>
public void ProcessRequest(HttpContext context)
{
throw new NotImplementedException();
}
#region IHttpAsyncHandler Members
/// <summary>Enables asynchronous processing of HTTP Web requests</summary>
/// <param name="context">An HttpContext object that provides references to the intrinsic server objects</param>
/// <param name="cb">The method to call when the asynchronous method call is complete. If callback is null, the delegate is not called.</param>
/// <param name="extraData"></param>
/// <returns>Any state data that is needed to process the request.</returns>
public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
{
Int32 someValueYouLikeToSendInYourClass = Convert.ToInt32(context.Request["Number"]);
Request request = new Request(cb, context);
request.Response.Number = someValueYouLikeToSendInYourClass;
Service.Singleton.AddRequest(request);
return request;
}
/// <summary>Provides an end method for an asynchronous process.</summary>
/// <param name="result">An object that contains information about the status of the process.</param>
public void EndProcessRequest(IAsyncResult result)
{
Request request = result as Request;
JavaScriptSerializer serializer = new JavaScriptSerializer();
request.HttpContext.Response.ContentType = "text/json";
request.HttpContext.Response.Write(serializer.Serialize(request.Response));
request.HttpContext.Response.End();
}
#endregion
#endregion
}
}
SUPPORTING CLASSES:
using System;
using System.Runtime.InteropServices;
namespace Concept.LongPolling.LongPolling
{
/// <summary>Represents the executable instance of an asynchronous operation.</summary>
[ComVisible(true)]
public interface IAsynchProcessor : IAsyncResult
{
/// <summary>
/// Gets a value that indicates whether the operation completed sucessfully.
/// </summary>
/// <returns>true if the operation completed sucessfully; otherwise, false.</returns>
bool ProcessRequest();
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Threading;
namespace Concept.LongPolling.LongPolling
{
public sealed class Service
{
#region CONSTRUCTORS
private Service()
{
requests = new List<IAsynchProcessor>();
backgroundThread = new Thread(new ThreadStart(MainLoop));
backgroundThread.IsBackground = true;
backgroundThread.Start();
}
#endregion
#region PROPERTIES
private static Service singleton;
private Thread backgroundThread;
private List<IAsynchProcessor> requests;
static readonly object padlock = new object();
public static Service Singleton
{
get
{
if (_singleton == null)
lock (_padlock)
{
if (_singleton == null)
_singleton = new Service();
}
return _singleton;
}
}
#endregion
#region METHODS
private void MainLoop()
{
while (true)
{
foreach (IAsynchProcessor request in requests.ToArray())
{
if (request.ProcessRequest())
requests.Remove(request);
}
Thread.Sleep(500);
}
}
public void AddRequest(IAsynchProcessor request)
{
lock (padlock)
{
requests.Add(request);
}
}
#endregion
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Concept.LongPolling.Business;
using System.Data;
namespace Concept.LongPolling.Handlers
{
public class Response
{
#region CONSTRUCTORS
public Response()
{
SessionValid = true;
Exception = String.Empty;
}
#endregion
#region PROPERTIES
public const int TimeOffset = 120;
public Int32 Number { get; set; }
public bool SessionValid { get; set; }
public String Exception { get; set; }
#endregion
#region METHODS
public void Generate()
{
// do some desired operation
Number += 1;
}
#endregion
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Concept.LongPolling.LongPolling;
namespace Concept.LongPolling.Handlers
{
public class Request : IAsynchProcessor
{
#region CONSTRUCTORS
public Request(AsyncCallback callback, HttpContext context)
{
asyncCallback = callback;
httpContext = context;
createdTime = DateTime.Now;
Response = new Response();
}
#endregion
#region PROPERTIES
public const int TimeoutSeconds = 15;
private AsyncCallback asyncCallback;
private HttpContext httpContext;
private DateTime createdTime;
public bool TimedOut
{
get
{
return ((DateTime.Now - createdTime).TotalSeconds >= TimeoutSeconds);
}
}
public Response Response { get; set; }
#region IAsyncResult Members
public HttpContext HttpContext
{
get
{
return httpContext;
}
}
public object AsyncState { get; set; }
System.Threading.WaitHandle IAsyncResult.AsyncWaitHandle
{
get { throw new NotImplementedException(); }
}
bool IAsyncResult.CompletedSynchronously
{
get { return false; }
}
public bool IsCompleted
{
get { return isCompleted; }
set
{
if (!value) return;
this.isCompleted = true;
asyncCallback(this);
}
}
bool isCompleted = false;
#endregion
#endregion
#region METHODS
public bool ProcessRequest()
{
this.Response = Controller.CreateResponse(this.Response);
this.IsCompleted = true;
return this.IsCompleted;
}
#endregion
}
}
Take a look at this article, which describes how to execute a method asynchronously, and uses an event handler that fires when the asynchronous method call has completed.
http://www.csharp-examples.net/create-asynchronous-method/
Here's a rough draft of how you would apply the contents of the article in your situation. I haven't tested the code, so it might not be perfect, but it should be close.
You need to import the following namespaces:
using System.Threading;
using System.ComponentModel;
using System.Runtime.Remoting.Messaging;
And here is the rough implementation:
//boolean flag which indicates whether the async task is running
private bool crawling = false;
private delegate bool CrawlWebsiteDelegate();
private bool CrawlWebsite()
{
//crawl the website
return false;
}
protected void Button1_Click(object sender, EventArgs e)
{
CrawlWebsiteDelegate worker = new CrawlWebsiteDelegate(CrawlWebsite);
AsyncCallback completedCallback = new AsyncCallback(CrawlWebsiteCompletedCallback);
if (!crawling)
{
worker.BeginInvoke(completedCallback, AsyncOperationManager.CreateOperation(null));
crawling = true;
}
}
private void CrawlWebsiteCompletedCallback(IAsyncResult ar)
{
//get the original worker delegate and the AsyncOperation instance
CrawlWebsiteDelegate worker = (CrawlWebsiteDelegate)((AsyncResult)ar).AsyncDelegate;
//finish the asynchronous operation
bool success = worker.EndInvoke(ar);
crawling = false;
if (success)
{
//perform sql tasks now that crawl has completed
}
}
EDIT: Here is the code in VB.NET - not positive that all syntax is correct
Private crawling As Boolean = False
Private Delegate Function CrawlWebsiteDelegate() As Boolean
Private Function CrawlWebsite() As Boolean
Return False
End Function
Protected Sub Button1_Click(sender As Object, e As EventArgs)
Dim worker As New CrawlWebsiteDelegate(AddressOf CrawlWebsite)
Dim completedCallback As New AsyncCallback(AddressOf CrawlWebsiteCompletedCallback)
If Not crawling Then
worker.BeginInvoke(completedCallback, AsyncOperationManager.CreateOperation(Nothing))
crawling = True
End If
End Sub
Private Sub CrawlWebsiteCompletedCallback(ar As IAsyncResult)
Dim worker As CrawlWebsiteDelegate = DirectCast(DirectCast(ar, AsyncResult).AsyncDelegate, CrawlWebsiteDelegate)
Dim success As Boolean = worker.EndInvoke(ar)
crawling = False
If success Then
DoSomeSqlTasks()
End If
End Sub
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