Spawn default browser with HTML string - html

Question

I have code (and for decades) that:
given some HTML string in memory
hand that document to an Internet Explorer object
and make Internet Explorer (separate process) visible
all without littering the user's computer with temporary files
In other words:
void SpawnIEWithSource(string szSourceHTML)
{
IWebBrowser ie = (IWebBrowser)CoCreateInstance(CLASS_InternetExplorer, null, CLSCTX_INPROC_SERVER | CLSCTX_LOCAL_SERVER,
UuidOf(IUnknown));
ie.Navigate2("about:blank");
ie.Document.Write(szSourceHtml);
ie.Document.Close;
ie.Visible = True;
}
Pros:
opens an HTML report out of process
does not create a temporary file
Cons:
hard-codes the use of Internet Explorer, rather than the user's preferred browser
But IE is going away
Microsoft recently announced that Internet Explorer (the product) will no longer come with Windows, but Internet Explorer (the programming api) will continue to work:
As announced today, Microsoft Edge with IE mode is officially replacing the Internet Explorer 11 desktop application on Windows 10. As a result, the Internet Explorer 11 desktop application will go out of support and be retired on June 15, 2022 for certain versions of Windows 10.
Out of scope at the time of this announcement (unaffected):
Internet Explorer mode in Microsoft Edge
Internet Explorer platform (MSHTML/Trident), including WebOC
Internet Explorer 11 desktop application on:
Windows 8.1
Windows 7 Extended Security Updates (ESU)
Windows 10 Server SAC (all versions)
Windows 10 IoT Long-Term Servicing Channel (LTSC) (all versions)
Windows 10 Server LTSC (all versions)
Windows 10 client LTSC (all versions)
What is the MSHTML (Trident) engine? How does that relate to IE mode?
The MSHTML (Trident) engine is the underlying platform for Internet Explorer 11. This is the same engine used by IE mode and it will continue to be supported (in other words, unaffected by this announcement). WebOC will also continue to be supported. If you have a custom or third-party app that relies on the MSHTML platform, you can expect it to continue to work.
(emphasis mine)
Which means that Microsoft is breaking 23 years of backwards compatibility - and replacing it with...nothing.
So i need to find a way to replace it.
spawn the default browser
give it HTML i want to display
all without temporary files
Bonus Reading
.NET: How to make WebBrowser control launch in IE, display HTML, out of process?
How to put the WebBrowser control into IE9 into standards?
How to start browser with html string with lua
Creating an IWebBrowser2 control

Answer 1

I'd encode HTML into Base64 and make it a Data-URI. All modern browsers are able to handle such URIs. This however won't work if your HTML string is too big.
Basically, it'd go like this:
string Base64Encode(string plainText) {
var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);
return System.Convert.ToBase64String(plainTextBytes);
}
void SpawnBrowserWithSource(string szSourceHTML) {
System.Diagnostics.Process.Start("data:text/html;base64," + Base64Encode(szSourceHTML));
}
Resulting in:
(code snippets are from the following Stackoverflow answers: base64 encoding and opening default browser)

Answer 2

If you know the user uses Chrome or Edge, you can replace the WebBrowser instance with ChromiumWebBrowser, and use the LoadHtml method to inject the content.
Relevant links:
web browser control in winform with google chrome c#
https://www.telerik.com/support/kb/winforms/details/how-to-embed-chrome-browser-in-a-winforms-application
https://cefsharp.github.io/api/51.0.0/html/T_CefSharp_WinForms_ChromiumWebBrowser.htm