SqlClient: Make SqlDataReader.GetFieldValue<XmlReader>() behave like GetXmlReader()

[bricelam]

Unfortunately, reader.GetFieldValue<XmlReader>(0) throws the following exception instead of coercing/wrapping the value inside of an XmlReader like calling reader.GetXmlReader(0) does.

System.InvalidCastException: Unable to cast object of type `'System.String' to type 'System.Xml.XmlReader'.

var connection = new SqlConnection(@"Data Source=(localdb)\MSSQLLocalDB");
connection.Open();

var command = connection.CreateCommand();
command.CommandText = "SELECT CAST('<data value=''test''/>' AS xml)";

var reader = command.ExecuteReader();
reader.Read();

// Works
var result1 = reader.GetXmlReader(0);

// Throws
var result2 = reader.GetFieldValue<XmlReader>(0);