How to set HTML to clipboard in C#?
When setting HTML text, you need to provide a header with additional information to what fragment of the html you actually want to paste while being able to provide additional styling around it:
Version:0.9
StartHTML:000125
EndHTML:000260
StartFragment:000209
EndFragment:000222
<HTML>
<head>
<title>HTML clipboard</title>
</head>
<body>
<!–StartFragment–><b>Hello!</b><!–EndFragment–>
</body>
</html>
With the header (and correct indexes), calling Clipboard.SetText with TextDataFormat.Html will do the trick.
To handle HTML and plain text pastes, you can’t use the Clipboard.SetText method, as it clears the clipboard each time it’s called; you need to create a DataObject instance, call its SetData method once with HTML and once with plain text, and then set the object to clipboard using Clipboard.SetDataObject.
Update
See "Setting HTML/Text to Clipboard revisited" for more details and ClipboardHelper implementation.
I found some code: https://www.experts-exchange.com/questions/21966855/Create-a-hyperlink-in-VB-net-copy-to-clipboard-Should-be-able-to-paste-hyperlink-in-Microsoft-Word-Excel.html
This code handles the problems of updating the start and end indexes.
Converted to c#:
public void AddHyperlinkToClipboard(string link, string description)
{
const string sContextStart = "<HTML><BODY><!--StartFragment -->";
const string sContextEnd = "<!--EndFragment --></BODY></HTML>";
const string m_sDescription = "Version:1.0" + Constants.vbCrLf + "StartHTML:aaaaaaaaaa" + Constants.vbCrLf + "EndHTML:bbbbbbbbbb" + Constants.vbCrLf + "StartFragment:cccccccccc" + Constants.vbCrLf + "EndFragment:dddddddddd" + Constants.vbCrLf;
string sHtmlFragment = "<A HREF=" + Strings.Chr(34) + link + Strings.Chr(34) + ">" + description + "</A>";
string sData = m_sDescription + sContextStart + sHtmlFragment + sContextEnd;
sData = sData.Replace("aaaaaaaaaa", m_sDescription.Length.ToString().PadLeft(10, '0'));
sData = sData.Replace("bbbbbbbbbb", sData.Length.ToString().PadLeft(10, '0'));
sData = sData.Replace("cccccccccc", (m_sDescription + sContextStart).Length.ToString().PadLeft(10, '0'));
sData = sData.Replace("dddddddddd", (m_sDescription + sContextStart + sHtmlFragment).Length.ToString().PadLeft(10, '0'));
sData.Dump();
Clipboard.SetDataObject(new DataObject(DataFormats.Html, sData), true );
}