How do I detect when the content of a WebBrowser control has changed (in design mode)?

Question

I'm using a WebBrowser control in design mode.

webBrowser1.DocumentText = "<html><body></body></html>";
doc = webBrowser1.Document.DomDocument as IHTMLDocument2;
doc.designMode = "On";

I have a save button that I would like to enable or disable depending on whether the contents of the control have changed.

I also need to know when the contents of the control have changed as I need to stop the user from navigating away from the control without accepting a confirmation message box stating that their changes will be lost.

I can't find any events that would let me know that the contents have changed.

Just don't. Design mode is for programmers, they have source control to clean up big messes. Spamming him with "are you sure" prompts is just annoying, he's sure 99.9% of the time. Write javascript if you want to do this anyway. — Hans Passant, Jun 21 '12 at 13:21
What do you mean? This is a WinForms app that lets the user edit some HTML content within a web browser control. They select what they're editing from a treeview and I need to confirm with them that they are aware that they will lose their changes if they try to navigate away without saving. It's not a web app. — crdx, Jun 21 '12 at 14:39

score 3 · Accepted Answer · answered Jun 21 '12 at 10:45

There is no such event since DocumentText is a simple string. I would create a string variable storing the last saved text and check it at each KeyDown / MouseDown / Navigating event.

string lastSaved;

private void Form_Load(object sender, System.EventArgs e)
{
   // Load the form then save WebBrowser text
   this.lastSaved = this.webBrowser1.DocumentText;
}

private void webBrowser1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
    // Check if it changed
    if (this.lastSaved != this.webBrowser1.DocumentText)
    {
        // TODO: changed, enable save button
        this.lastSaved = this.webBrowser1.DocumentText;
    }
}

private void webBrowser1_Navigating(object sender, WebBrowserNavigatingEventArgs e)
{
    // Check if it changed
    if (this.lastSaved != this.webBrowser1.DocumentText)
    {
        // TODO: ask user if he wants to save
        // You can set e.Cancel = true to cancel loading the next page
    }
}

I don't see a KeyDown event for the System.Windows.Forms.WebBrowser - the only key event it supports is PreviewKeyDown. — Scott Baker, Jul 23 '14 at 17:58
This doesn't take into account if there is `TAB` or arrow keys pressed. Also it doesn't register change when images are resized, moved etc. See my solution. — Coder12345, Jun 04 '21 at 20:42

score 3 · Answer 2 · edited Jun 04 '21 at 20:50

3

QueryInterface() the document for IMarkupContainer2, then call IMarkupContainer2::RegisterForDirtyRange with your own implementation of IHTMLChangeSink. Your IHTMLChangeSink::Notify implementation will be called when a change is made.

Note: Do this after you set the design mode. The document gets reloaded and event hook get lost, if you toggle the design mode.

edited Jun 04 '21 at 20:50

Coder12345

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answered Jun 22 '12 at 19:46

Sheng Jiang 蒋晟

15,125
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This sounds like a good implementation, but it's a little too abstract for my skill level. Could you give a code example? – Scott Baker Jul 23 '14 at 17:26

score 0 · Answer 3 · answered Mar 07 '20 at 13:35

0

another solution, if you implement IDocHostUIHandler, you can use its method UpdateUI

answered Mar 07 '20 at 13:35

Lenor

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Coder12345 · Answer 4 · 2021-06-04T21:03:15.953

This seems to work - QueryInterface() for IPersistFile interface and use IPersistFile::IsDirty method with the return value of S_OK (if dirty or if the design mode document has been modified).

You don't need to use IPersistFile::Load to load the contents into the web browser, WebBrowser->Navigate() will also work fine.

Note - there is a same IsDirty() method also in IPersistStream and IPersistStreamInit interfaces

I don't use C# but it should be relatively easy to rewrite.

bool IsEditorDirty(WebBrowser* WB)
    {
    // beware, if it fails to get Document and IPersistFile it will not register as dirty
    bool isdirty = false;

    IHTMLDocument2* pDoc2 = WB->Document;

    if (pDoc2) {
        IPersistFile* pPFile;

        if (pDoc2->QueryInterface(IID_IPersistFile, (void**)&diPFile) == S_OK) {
            isdirty = (pPFile->IsDirty() == S_OK);
            pPFile->Release();
            }
    
        pDoc2->Release();
        }

    return isdirty;
    }

How do I detect when the content of a WebBrowser control has changed (in design mode)?

4 Answers4

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