Description

Loading some RTF in a RichTextBox, saving it and loading it again causes an exception to be thrown.

This happens because the RTF contains a hyperlink which contains an umlaut ("ö" in this example).
That umlaut is correctly escaped in the source RTF with "'f6".
Loading the source RTF works fine.
Saving the RTF with RichTextBox causes the correctly escaped text to become 'f6.
Loading this again causes an exception while trying to construct the NavigationUri, as an unescaped "'" is not valid in an URI.

After some investigation the issue seems to be that:
XamlToRtfWriter.WriteInlineChild calls BamlResourceContentUtil.UnescapeString which then simply removes the "\" before the "'", thus producing an invalid URI.

One way to solve this would be to add

else if (documentNode.NavigateUri[i] == "'")
{
    _rtfBuilder.Append("\\'");
}

Reproduction Steps

See attached repro project.
UmlautIssue.zip

Expected behavior

No exception should occur and RTF should be rendered.

Actual behavior

Exception is thrown during load (after save from RichTextBox).

Regression?

No response

Known Workarounds

No response

Impact

No response

Configuration

Tested with .NET 4.8 and .NET 6.0.

Other information

No response