problem reading child by attribute

[C# Programming]

I am using this code to read one the childs using its attribule but it's always reading the first child though the selected GUID is the last child? what's the problem:

xml_documen.SelectSingleNode("/Resume/Contacts/Contact[@ID='73298407-06fa-462a-be30-254a5318176c']");

txtContactNumber.Text = xml_documen.GetElementsByTagName("Number")[0].InnerText;