XmlException : that is hexadecimal exceptiom

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C#

ASP.NET

exception isSystem.Xml.XmlException: 'here is one special character like |', hexadecimal value 0x19, is an invalid character at line 1.

I am using this query to delete the all duplicate records based on link tag, link tag is unique.

doc.Root.Elements("item")
               .GroupBy(s => (string)s.Element("Link"))
               .SelectMany(g => g.Skip(1))
               .Remove();

Is there any possible to remove hexadecimalvalus and replace with some other text.
and
Is there any possible to remove entire record also.

Please Help me....

Thank you....