How to inject CSS in WebBrowser control?

by

I didn’t try this myself but since CSS style rules can be included in a document using the <style> tag as in:

<html>
<head>
<style type="text/css">
    h1 {color:red}
    p {color:blue}
</style>
</head>

you could try giving:

HtmlElement head = webBrowser1.Document.GetElementsByTagName("head")[0];
HtmlElement styleEl = webBrowser1.Document.CreateElement("style");
IHTMLStyleElement element = (IHTMLStyleElement)styleEl.DomElement;
IHTMLStyleSheetElement styleSheet = element.styleSheet;
styleSheet.cssText = @"h1 { color: red }";
head.AppendChild(styleEl);

a go. You can find more info on the IHTMLStyleElement here.

Edit

It seems the answer is much much simpler than I originally thought:

  using mshtml;

  IHTMLDocument2 doc = (webBrowser1.Document.DomDocument) as IHTMLDocument2;
  // The first parameter is the url, the second is the index of the added style sheet.
  IHTMLStyleSheet ss = doc.createStyleSheet("", 0);

  // Now that you have the style sheet you have a few options:
  // 1. You can just set the content as text.
  ss.cssText = @"h1 { color: blue; }";
  // 2. You can add/remove style rules.
  int index = ss.addRule("h1", "color: red;");
  ss.removeRule(index);
  // You can even walk over the rules using "ss.rules" and modify them.

I wrote a small test project to verify that this works. I arrived at this final result by doing a search on MSDN for IHTMLStyleSheet, upon which I happened across this page, this page and this one.

More Related Contents:

  1. How can I get the WebBrowser control to show modern contents?
  2. How to inject Javascript in WebBrowser control?
  3. Replacing .NET WebBrowser control with a better browser, like Chrome? [closed]
  4. How to get an HtmlElement value inside Frames/IFrames?
  5. Disable JavaScript error in WebBrowser control
  6. Open link in new TAB (WebBrowser Control)
  7. Interaction between WebBrowser Control and Windows Forms
  8. Use cookies from CookieContainer in WebBrowser
  9. Prevent from displaying of Windows Security window
  10. WebBrowser control and JavaScript errors
  11. Uploading Files Not Working – Need Assistance
  12. How to get ALL child controls of a Windows Forms form of a specific type (Button/Textbox)?
  13. Question about terminating a thread cleanly in .NET
  14. Word wrap for a label in Windows Forms
  15. How to make two transparent layer with c#?
  16. TabControl with Close and Add Button
  17. WebBrowser.DrawToBitmap() or other methods?
  18. Keep window on top and steal focus in WinForms
  19. How do I change the culture of a WinForms application at runtime
  20. C# Form.TransparencyKey working different for different colors, why?
  21. Drawing on top of controls inside a panel (C# WinForms)
  22. How can I display a loading control while a process is waiting for be finished?
  23. How do you resize a form to fit its content automatically?
  24. Get ReadyState from WebBrowser control without DoEvents
  25. Why is my bound DataGridView throwing an “Operation not valid because it results in a reentrant call to the SetCurrentCellAddressCore function” error?
  26. Toggle switch control in Windows Forms
  27. WinForms DataGridView – databind to an object with a list property (variable number of columns)
  28. How do I prevent print screen
  29. Process.Start(url) fails
  30. How to use dependency injection in WinForms

Leave a Comment