Webbrowser Control - No CSS Applied

Injecting CSS in WebBrowser Control

What I did to get it working

        CurrentDocument = (mshtml.HTMLDocument)webBrowser1.Document.DomDocument;
        styleSheet = CurrentDocument.createStyleSheet("", 0);

        StreamReader streamReader = new StreamReader(@"test.css"); //test.css is Stylesheet file
        string text = streamReader.ReadToEnd();
        streamReader.Close();
        styleSheet.cssText = text;

How to inject CSS in WebBrowser Control

What are you trying to reference with IHTMLStyleElement and IHTMLStyleSheetElement? Its not anywhere in the .NET framework.

Just modify your code to write the contents of the generic HtmlElement type instead by writing the contents of the .InnerText or .InnerHtml with your stylesheet

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        webBrowser1.Navigate("https://www.aparat.com/aleffamily/live2");
        webBrowser1.DocumentCompleted += webBrowser1_DocumentCompleted;
    }

    private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
    {

        HtmlElement head = webBrowser1.Document.GetElementsByTagName("head")[0];
        HtmlElement styleEl = webBrowser1.Document.CreateElement("style");
        styleEl.InnerHtml = @"body {background-color:transparent !important; margin: 0px auto; overflow: hidden; }.live__content{display:none;}.chat__footer{display:none;}.chat__header{display:none}#header{display:none}.in-chat-avatar{display:none}.message__username{font-style:italic;font-weight: 800!important;color:ff8f0f !important}.message__text{font-style:italic;font-weight: 400!important;color:ff8f0f !important}.chat__content{ background-color:transparent  !important}.chat{ background-color:transparent  !important}";
        head.AppendChild(styleEl);

    }
}

WebBrowser component not showing CSS 3

Just for further reference to other people needing this:

First of all:
Thanks to Boo & Lex Li
For helping me find the answer to my question.

You have to set a certain registry to the right value:

There are two different sets of keys for 32 bit and 64 bit applications.

32 bit:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_BROWSER_EMULATION

Value Key: yourapplication.exe

64 bit:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_BROWSER_EMULATION

Value Key: yourapplication.exe

The value to set this key to is (taken from MSDN here) as decimal values:

9999 (0x270F)
Internet Explorer 9. Webpages are displayed in IE9 Standards mode, regardless of the  !DOCTYPE directive.

 9000 (0x2328)
 Internet Explorer 9. Webpages containing standards-based !DOCTYPE directives are displayed in IE9 mode.

8888 (0x22B8)
Webpages are displayed in IE8 Standards mode, regardless of the !DOCTYPE directive.

8000 (0x1F40)
Webpages containing standards-based !DOCTYPE directives are displayed in IE8 mode.

7000 (0x1B58)
Webpages containing standards-based !DOCTYPE directives are displayed in IE7 Standards mode.

Even tough MSDn claims that 9000 is the automatically assigned value. Apperently this is simply not true.

Below you can find the code how to add these keys to your registry. Please not that your application has a different processname when you debug.

RegistryKey key = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_BROWSER_EMULATION", true);
        if (key != null)
        {
            key.SetValue("YourApplicationName.exe", 9000, RegistryValueKind.DWord);
        }

        key = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_BROWSER_EMULATION", true);
        if (key != null)
        {
            key.SetValue("YourApplicationName.exe", 9000, RegistryValueKind.DWord);
        }

So thanks all and Good Luck

Edit: User Account Control should be off to make this code work.

wpf webbrowser control not applying css

In your constructor, you can write these lines of code in order to resolve issues with your CSS:

var fileName = System.IO.Path.GetFileName(Process.GetCurrentProcess().MainModule.FileName);
SetBrowserFeatureControlKey("FEATURE_BROWSER_EMULATION", fileName, GetBrowserEmulationMode());  

Alternatively, you can read this blog post. And this forum post, that contains some hacks for your trouble.

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