I copied and pasted what you have provided into a file named "test.xml" (of course removed that extra dash from second line)
and tested this code :
XmlDocument rawXMLData = new XmlDocument();
StreamReader reader = new StreamReader(@"d:\test.xml");
rawXMLData.LoadXml(reader.ReadToEnd());
var result = rawXMLData.SelectNodes("ROOT/tblmembers/additionalinfo/patientadditionalinfo[@id='1']/race");
foreach (XmlNode node in result)
Console.WriteLine(node.Name + " = " + node.InnerText);
Console.ReadLine();
And it prints :
race = C
However I can write the XPath but I took the XPath from Pallini's answer ;)
Hope it helps.