The HtmlPreview parameter is used in RadRichTextBox for Silverlight to visualize the Print preview of the document. This option, along with HTML printing, were introduced to work around a performance problem with the default printing mechanism of Silverlight 4. RadRichTextBox for WPF does not support Print Preview and you can pass only Native
as a parameter to the PrintCommand. Every other string is not a valid command parameter. We have this feature already logged in our backlog and I just created a public item
in the feedback portal, which you can vote and subscribe in order to receive updates on the matter.
If you need a preview, you can easily implement one - just create another RadRichTextBox, which is read only and show the document in it.
Let me know if there is anything else I can assist you with.
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