XML Deserialize error

System.InvalidOperationException: There is an error in XML document (4, 2).
 ---> System.InvalidOperationException: <database xmlns='http://www.iw.com/sns/platform/'> was not expected.

var serializer = new XmlSerializer(typeof(XmlUtils));
var reader = XmlReader.Create("test.xml", new XmlReaderSettings
{
    IgnoreComments = true,
    IgnoreWhitespace = true,
    LineNumberOffset = 2,
    IgnoreProcessingInstructions = true,
});
serializer.Deserialize(reader);

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<tns:database xmlns:tns="http://www.iw.com/sns/platform/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <Group id="function_on">
        <ItemSpec id="test" open="true">
    </Group>
</tns:database>