Comparing a XML doc to SQL Server

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C#

database

How do i go about comparing the content of a Database table to that of an XML document. If there are any difference in the XML to whats stored in the table do an update in the table. If no difference is found in the XML then the content in the table will remain the same.

Eg
--XML Document----

<Root>
<Firstname>John</Firstname>
<Surname>Smith</Surname>
</Root>

-- Table----

Firstname|  Surname
---------------------
  John   |  bent

-- Table Changed to --

Firstname|  Surname
---------------------
  John   |  Smith