I have a webpage, and an input button on it. Clicking on this button, in a specific div are loaded some data. My problem is that I can't catch this data.
The following code is my attempt to solve this problem, but without success.
private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
HtmlElement div_result = webBrowser1.Document.GetElementById("div_result");
div_result.AttachEventHandler("onpropertychange", new EventHandler(resultEventHandler));
}
private void resultEventHandler(object sender, EventArgs e)
{
MessageBox.Show("Loaded");
}
If I click on input button, div's content is modified, but the resultEventHandler does not fire.
So, I have two questions:
Where is my fault in this code?
Is there a "normal way"(I mean without using timers or Aplication.DoEvents()) to work with ajax using WebBrowser control in C#?
Changing the innerText or innerHTML of child elements will not cause the onpropertychange event to fire for the parent element.
I cannot tell why HtmlElement events do not work for you. But I had the same problem and resolved it by using COM wrappers:
mshtml.HTMLDocumentClass doc = (mshtml.HTMLDocumentClass)webBrowser1.Document.DomDocument;
mshtml.IHTMLElement2 div_result = (mshtml.IHTMLElement2)doc.getElementById("div_result");
mshtml.HTMLElementEvents2_Event events = (mshtml.HTMLElementEvents2_Event)div_result;
events.onpropertychange += resultEventHandler;
This may be too late but here it is anyways in case you are still wondering:
1 - HtmlElement div_result = webBrowser1.Document.GetElementById("div_result");
Line #1 executes when the web page has loaded and the DocumentCompleted event has been called by the browser. Inside the event handler you first retrieve a pointer to the DOM element "div_result" and you assign an HtmlElement type variable named div_result.
2 - div_result.AttachEventHandler("onpropertychange", new EventHandler(resultEventHandler));
Line #2 - registers the "onpropertychange" event and assigns the method resultEventHandler as the listener method.
Every time you click on the button on your web page, the button (which I assume) is in a form that gets submitted which causes the web page to load; by the way you did not specify which post method you are using when the button is clicked (get or post). When the web page download completes and the DOM element tree is constructed your DocumentCompleted event is called. You're DocumentCompleted event handler method performed the instructions described above.
Every time you click your button, you web page is reloaded and you reassign the event listener for the onpropertychange event. You are only assigning the event listener. The event will never be called. It will just be defined every time you click the button. You have a classic which came first chicken, or egg problem. But in your case, your chicken is the button click event causing the DocumentCompleted method to run which resets the state of all variables in the method, and your egg is wanting a pointer to the DIV element's onpropertychange event before the button is clicked on the web page . How do you assign an event listener to an htmlelement before you can get a pointer from the DOM which has not been constructed? Put a Boolean flag variable in the class that contains the DocumentCompleted method and set its initial state. Move the div_result variable outside of the DocumentCompleted method to increase its scope and to save its state across a button click event. This way, you will get a pointer to your div element and set its onpropertychange event listener the first time the web page is downloaded. Add a test if you just want to set a pointer to the DIV element's onpropertychange event listener just once (I put one in the sample code below), and the next time you click your button, your event will fire. NOTE! Make sure you do not add, or delete any element to your web page after you store a pointer to any of the web page's elements or their events. Otherwise you will have to reparse the DOM to get a pointer to the Element's new position in the DOM tree.
//See below:
class SomeClass
{
bool DocumentHasLoaded = false;
HtmlElement div_result = null;
//Constructor and other methods go here....
//Then change your DocumentCompleted method to look like this:
private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
if (DocumentHasLoaded == false) // I prefer using a ! before the variable instead
{
DocumentHasLoaded = true; // You will have to create your own appropriately timed mechanism to reset this variable's state should you want to execute the whole process again.
div_result = webBrowser1.Document.GetElementById("div_result");
div_result.AttachEventHandler("onpropertychange", new EventHandler(resultEventHandler));
}
}
}
In order to answer your second question I require more information about the data that is loaded in the DIV; e.g. where it comes from and what type it is plus any other pertinent information you can think of.
Related
I have a C# 4.0 WinForms application, which has a WebBrowser control and 2-buttons.
Clicking the first button sends a URL to the browser to navigate to a specified webSite.
Clicking the second button parses the OuterHtml of the webBrowser1.Document, looking for an "https://..." link for File Download.
The code then uses a webClient.DownloadFileAsync to pull down a file for further use in the application.
The above code successfully works, if I manually click those buttons.
In an effort to automate this for the end-user, I place the first button's click event, i.e. btnDisplayWeb.PerformClick(); in the form's Form1_Load event. This also works, allowing the webBrowser1 to populate its Document with the desired webSite.
However, I am unable to programatically click the 2nd button to acquire the web link for file download.
I have tried to place the 2nd buttons click event within the browser's DocumentCompleted event, as shown below.
private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
btnMyUrl.PerformClick();
}
However, from what I've read on StackOverFlow and other sites, it's possible that this particular event gets called more than once, and hence it fails.
I've also attempted to loop for a number of seconds, or even use a Thread.Sleep(xxxx), but the browser window fails to populate until the sleep or timer stops.
I attempted to use the suggestions found on the following StackOverFlow site shown below.
How to use WebBrowser control DocumentCompleted event in C#?
private void webBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
string url = e.Url.ToString();
if (!(url.StartsWith("http://") || url.StartsWith("https://")))
{
// in AJAX
}
if (e.Url.AbsolutePath != this.webBrowser.Url.AbsolutePath)
{
// IFRAME
}
else
{
// REAL DOCUMENT COMPLETE
}
}
However, in parsing the OuterHtml, nothing is returned in the first two sections, and in the third section, other elements are returned instead of the desired "https://..." link for File Download.
Interestingly, if I use a webBrowser1.ReadyState event, as shown below, and place a MessageBox inside DocumentCompleted, this seems to allow the browser document to complete, because after clicking the OK button, the parsing is successful.
if (webBrowser1.ReadyState == WebBrowserReadyState.Complete)
{
MessageBox.Show("waiting", "CHECKING");
btnMyUrl.PerformClick();
}
However, I then have the difficulty of finding a way to click the OK button of the MessageBox.
Is there another event that occurs after the DocumentCompleted event.
OR, can someone suggest how to programmatically close the MessageBox?
If this can be done in code, then I can perform the buttonClick() of the 2nd button in that section of code.
After finding that the addition of a MessageBox allows the webBrowser1.Document to complete, and using webBrowser1.ReadyState event within the webBrowser_DocumentCompleted event, all I needed to do, was to find a way to programmatically close the MessageBox.
Further searching on StackOverFlow revealed the following solution on the site below.
Close a MessageBox after several seconds
Implementing the AutoClosingMessageBox, and setting a time interval, closed the MessageBox and allowed my button click, i.e. btnMyUrl.PerformClick(); to successfully parse the OuterHtml and now the code works properly.
Hopefully, if someone else discovers that placing a MessageBox within the webBrowser_DocumentCompleted event allows the document to complete; the aforementioned AutoClosingMessageBox will assist them as well.
This question already has answers here:
dynamically created button click event not firing
(5 answers)
Closed 8 years ago.
I have some buttons that are being dynamically added to an asp.net page. However the onclick event is not being fired. Here is the code for it being added and it is ran when the page loads. I am very new to ASP.NET so I am sure I am making some basic errors. TIA.
protected void Page_Load(object sender, EventArgs e)
{
FillTable();
string rownum = (goalstable.Rows.Count).ToString();
Button bt = new Button();
bt.Text = "View";
bt.ID = (rownum);
bt.CssClass = "button";
bt.Click += Viewbutton_Click;
goalstable.Rows[1].Cells[0].Controls.Add(bt);
}
FillTable() is a method that fills a table from an SQL DB.
The on click event for the button that has been added.
protected void Viewbutton_Click(object sender, EventArgs e)
{
getGID();
setGoalDets();
goals.Style.Add("display", "block");
darkLayer2.Style.Add("display", "block");
}
Any Ideas what I may be doing wrong.
In a nutshell, you need to add the button earlier in the Page lifecycle, before the Page_Load event.
What's happening is every server event — even simple button clicks — is a new HTTP request to your page. In turn, every HTTP request for your page results in a completely new-from-scratch C# page object. Therefore you start with a brand new Page object and a brand new ViewButton when the click event for your ViewButton is triggered.
To make things work correctly, so the new page has the same properties as the old, ASP.Net relies on a feature called ViewState. ViewState information is (typically) submitted with the http request from the client's browser, and is used to build a new Page object with the same Controls and property values as the old one.
Here's the trick: ViewState is restored for the page before the load event is processed. If the button does not exist yet at the time the ViewState is restored, that information is thrown away, and the page will not later know it needs to raise the click event (or rather, it will think there there is no button for the click event code to run in the first place).
Therefore, you need to move the code to create your button to the Pre_Init event, which runs before the ViewState is restored.
When working with "dynamic" controls in ASP.Net WebForms, I often find it easier to just add a reasonable number of controls to the page in a static manner and set them all so that their Visible property is false. Then at runtime I will set Visible back to true for just the controls that I need.
How can I detect when a System.Windows.Forms.WebBrowser control has completed loading?
I tried to use the Navigate and DocumentCompleted events but both of them were raised a few times during document loading!
I think the DocumentCompleted event will get fired for all child documents that are loaded as well (like JS and CSS, for example). You could look at the WebBrowserDocumentCompletedEventArgs in DocumentCompleted and check the Url property and compare that to the Url of the main page.
I did the following:
void BrowserDocumentCompleted(object sender,
WebBrowserDocumentCompletedEventArgs e)
{
if (e.Url.AbsolutePath != (sender as WebBrowser).Url.AbsolutePath)
return;
//The page is finished loading
}
The last page loaded tends to be the one navigated to, so this should work.
From here.
The following should work.
private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
//Check if page is fully loaded or not
if (this.webBrowser1.ReadyState != WebBrowserReadyState.Complete)
return;
else
//Action to be taken on page loading completion
}
Note the url in DocumentCompleted can be different than navigating url due to server transfer or url normalization (e.g. you navigate to www.microsoft.com and got http://www.microsoft.com in documentcomplete)
In pages with no frames, this event fires one time after loading is complete. In pages with multiple frames, this event fires for each navigating frame (note navigation is supported inside a frame, for instance clicking a link in a frame could navigate the frame to another page). The highest level navigating frame, which may or may not be the top level browser, fires the final DocumentComplete event.
In native code you would compare the sender of the DocumentComplete event to determine if the event is the final event in the navigation or not. However in Windows Forms the sender parameter is not wrapped by WebBrowserDocumentCompletedEventArgs. You can either sink the native event to get the parameter's value, or check the readystate property of the browser or frame documents in the DocumentCompleted event handler to see if all frames are in the ready state.
There is a prolblem with the readystate method as if a download manager is present and the navigation is to a downloadable file, the navigation could be cancelled by the download manager and the readystate won't become complete.
I had the same issue of multiple DocumentCompleted fired events and tried out all the suggestions above. Finally, seems that in my case neither IsBusy property works right nor Url property, but the ReadyState seems to be what I needed, because it has the status 'Interactive' while loading the multiple frames and it gets the status 'Complete' only after loading the last one. Thus, I know when the page is fully loaded with all its components.
I hope this may help others too :)
It doesn't seem to trigger DocumentCompleted/Navigated events for external Javascript or CSS files, but it will for iframes. As PK says, compare the WebBrowserDocumentCompletedEventArgs.Url property (I don't have the karma to make a comment yet).
If you're using WPF there is a LoadCompleted event.
If it's Windows.Forms, the DocumentCompleted event should be the correct one. If the page you're loading has frames, your WebBrowser control will fire the DocumentCompleted event for each frame (see here for more details). I would suggest checking the IsBusy property each time the event is fired and if it is false then your page is fully done loading.
Using the DocumentCompleted event with a page with multiple nested frames didn't work for me.
I used the Interop.SHDocVW library to cast the WebBrowser control like this:
public class webControlWrapper
{
private bool _complete;
private WebBrowser _webBrowserControl;
public webControlWrapper(WebBrowser webBrowserControl)
{
_webBrowserControl = webBrowserControl;
}
public void NavigateAndWaitForComplete(string url)
{
_complete = false;
_webBrowserControl.Navigate(url);
var webBrowser = (SHDocVw.WebBrowser) _webBrowserControl.ActiveXInstance;
if (webBrowser != null)
webBrowser.DocumentComplete += WebControl_DocumentComplete;
//Wait until page is complete
while (!_complete)
{
Application.DoEvents();
}
}
private void WebControl_DocumentComplete(object pDisp, ref object URL)
{
// Test if it's the main frame who called the event.
if (pDisp == _webBrowserControl.ActiveXInstance)
_complete = true;
}
This code works for me when navigating to a defined URL using the webBrowserControl.Navigate(url) method, but I don't know how to control page complete when a html button is clicked using the htmlElement.InvokeMember("click").
You can use the event ProgressChanged ; the last time it is raised will indicate that the document is fully rendered:
this.webBrowser.ProgressChanged += new
WebBrowserProgressChangedEventHandler(webBrowser_ProgressChanged);
Background: I am customizing an existing ASP .NET / C# application. It has it's own little "framework" and conventions for developers to follow when extending/customizing its functionality. I am currently extending some of it's administrative functionality, to which the framework provides a contract to enforce implementation of the GetAdministrationInterface() method, which returns System.Web.UI.Control. This method is called during the Page_Load() method of the page hosting the GUI interface.
Problem: I have three buttons in my GUI, each of which have been assigned an Event Handler. My administration GUI loads up perfectly fine, but clicking any of the buttons doesn't do what I expect them to do. However, when I click them a second time, the buttons work.
I placed breakpoints at the beginning of each event handler method and stepped through my code. On the first click, none of the event handlers were triggered. On the second click, they fired.
Any ideas?
Example of Button Definition (within GetAdministrationInterface)
public override Control GetAdministrationInterface()
{
// more code...
Button btn = new Button();
btn.Text = "Click Me!";
btn.Click += new EventHandler(Btn_Click);
// more code...
}
Example of Event Handler Method Definition
void Btn_Click(object sender, EventArgs e)
{
// Do Something
}
Page_Load Method that calls GetAdministrationInterface
protected void Page_Load(object sender, System.EventArgs e)
{
if (!Page.IsAsync)
{
List<AdministrationInterface> interfaces = <DATABASE CALL>;
foreach(AdministrationInteface ai in interfaces)
{
placeholderDiv.Controls.Add(ai.GetAdministrationInterface());
}
}
}
Good grief! I knew it was going to be something this stupid. Purely my fault of course and my lack of knowledge in ASP .NET.
After doing a multitude of Google searches and eventually being blocked by Google on suspicion of being a bot running automated scripts, I managed to squeeze in one last search in and stumbled across this article. Already at the point of giving up, I tried my best to read the article without skipping 10 lines at a time or looking for pretty pictures. In the section titled Assigning IDs to Dynamically Created Controls, I read these magical and most joyful words:
If you view the source HTML before you click the not-working button and after you have clicked it, you will notice a small difference. The buttons have different HTML IDs before and after the post-back. I got ctl04 and ctl05 before the post-back and ctl02 and ctl03 after the post-back.
ASP.NET button recognizes events by checking for a value for its ID in the Request.Form collection. (In truth it happens differently and controls do not check Request.Form collection by themselves. Page passes post data to controls by their IDs and to controls that are registered to be notified about post data). ASP.NET does not fire the Click event, because the button's ID has changed between the post-backs. The button you have clicked and the button you see after are different buttons for ASP.NET.
Sure enough, when I viewed the HTML the first time, my button had the ID ctl04$ctl36. After clicking the button, my button had the ID ctl04$ctl33.
So there you have it! All I had to do was set the ID on the buttons and presto! My event handlers are now being called!
Sample Solution:
public override Control GetAdministrationInterface()
{
// more code...
Button btn = new Button();
btn.Text = "Click Me!";
// !!THE BANE OF MY EXISTENCE!!
btn.ID = "The_Bane_of_My_Existence";
// !!THE BANE OF MY EXISTENCE!!
btn.Click += new EventHandler(Btn_Click);
// more code...
}
What a great way to spend two days...
I had the same problem, but the accepted answer here was not causing it. I had a text box and a search button, and clicking the button the first time didn't perform the search. The event handler of the button wasn't being hit. But clicking the button a second time did trigger the event on the server. Here is why:
If you have an <asp:Textbox> with its AutoPostBack set to true, after typing in the text box and then moving to click a button, the text box causes a post-back immediately the moment it loses focus. So the click even of the button doesn't count (the page is already posted-back as a result of the text box's event). That's why when you click the button a second time, it works because the text box is not involved in the second post-back.
Set the AutoPostBackproperty of the <asp:Textbox> to false to fix this issue.
A quick fix is to set an ID to the ASCX control your are loading on a page. For example, if your code is like this:
UserControl SpecsControl = (UserControl)Page.LoadControl("../name.ascx");
SpecsContainer.Controls.Add(SpecsControl);
then you need to add a line (before Controls.Add):
SpecsControl.ID = "Aribtrary_Name";
Then your handler method is fired at the first click.
I was facing the same problem. My button froze after my first click. For me this annoying problem got solved when I disabled the button's EnableViewState attribute.
For me it was the UpdatePanel , my Button and my TextBox were both inside an UpdatePanel , so when I post-back , it caused some weird behavior . It took it outside of the UpdatePanel and that fixed it .
Even i had the same problem. the cause was "localhost:1656/secure/login.aspx?ReturnUrl=%2f".
if the request contain %2f as query string, the first post will not be succeeded even though "%2f" is representing "/".
one way to avoid this by having a condition check in pageload
protected void Page_Load(object sender, EventArgs e)
{
string queryString = Request.QueryString.ToString();
if(queryString == "ReturnUrl=%2f")
{
Response.Redirect("/secure/login.aspx");
}
}
Whilst its hard to know exactly without seeing the full Page_load method it does smell a little bit like the event handlers are not hooking up until the page is reloaded.
eg:
if (IsPostBack) {
// Add handlers here ...
}
I had same problem. And I searched on internet i didnt find a solution. After that i found sample code and I used it. It worked for me. Web site link is below:
http://www.c-sharpcorner.com/UploadFile/abhikumarvatsa/calling-an-Asp-Net-C-Sharp-method-web-method-using-javascript/
I have a page and a user control — we'll call them Detail.aspx and Selector.ascx.
Let's say the page shows the details of individual records in a database. The user control basically consists of a DropDownList control and some associated HTML. The DropDownList displays a list of other records to switch to at any time.
When the DropDownList fires its SelectedIndexChanged event, I'd like the parent page, Detail.aspx in this case, to handle it. After all, he'll need to know what was selected so that he can appropriately change the URL and the details shown, etc.
To do that, I've done what I usually do, which is also what the top answer says to do in this StackOverflow question:
public event EventHandler DropDownSelectedIndexChanged
{
add
{
MyDropDownList.SelectedIndexChanged += value;
}
remove
{
MyDropDownList.SelectedIndexChanged -= value;
}
}
The above code appears in the Selector.ascx.cs codebehind file.
As a result, on Detail.aspx, I can use it like so:
<cc1:RecordSelector ID="RecordSelector1" runat="server"
OnDropDownSelectedIndexChanged="RecordSelector1_DropDownSelectedIndexChanged" />
So far nothing fancy or surprising.
Here is my problem:
This causes a NullReferenceException when the browser hits Detail.aspx.
Debugging the problem shows that when the page is first hit, the public event I've shown above tries to add the event, but MyDropDownList is null, thus throwing the exception. From what I can tell, the events are added (or attempted to be added) before the Selector user control's Load event fires and thus also before the DropDownList's Load event fires.
Curiously, if I omit the OnDropDownSelectedIndexChanged attribute from Detail.aspx and instead put the following in the Page_Load event in Detail.aspx.cs:
protected void Page_Load(object sender, EventArgs e)
{
RecordSelector1.DropDownSelectedIndexChanged += new EventHandler(RecordSelector1_DropDownSelectedIndexChanged);
}
It works exactly as expected. The events are attached and handled just fine. No problems.
But this means several bad things:
I have to remember not to use the designer to add said event onto my user control
I have to remember not to add the event via attributes when working in source view
Worst of all, as the control's author I need to make sure everybody else using my control knows 1 and 2
So what am I doing wrong? Every example I've seen thus far shows similar usage of exposing child controls' events through a user control.
The reason this works:
protected void Page_Load(object sender, EventArgs e)
{
RecordSelector1.DropDownSelectedIndexChanged
+= new EventHandler(RecordSelector1_DropDownSelectedIndexChanged);
}
and this does not:
<cc1:RecordSelector ID="RecordSelector1" runat="server"
OnDropDownSelectedIndexChanged="RecordSelector1_DropDownSelectedIndexChanged" />
is because the first one adds the handler after the control has been initialized (via the page's Init). The second example gets parsed much earlier and as such the page is attempting to add the handler before the control has initialized.
Due to the nature of the page's life cycle I think you may have to live with adding the event handler in the code-behind. There will be no way to add the handler before the control is initialized because that control will always be null prior to initialization.