How to solve “unable to switch the encoding” error when inserting XML into SQL Server

Question

I\'m trying to insert into XML column (SQL SERVER 2008 R2), but the server\'s complaining:

System.Data.SqlClient.SqlException (0x80131904):
XML

Answer 1

Isn't the easiest solution to tell the serializer not to ouput the XML declaration? .NET and SQL should sort the rest out between them.

        XmlSerializer serializer = new XmlSerializer(typeof(MyMessage));
        StringWriter str = new StringWriter();
        using (XmlWriter writer = XmlWriter.Create(str, new XmlWriterSettings { OmitXmlDeclaration = true }))
        {
            serializer.Serialize(writer, message);
        }
        string messageToLog = str.ToString();

Answer 2

It took me forever to re-solve this problem.

I was doing an INSERT statement into SQL Server as something like:

UPDATE Customers 
SET data = '<?xml version="1.0" encoding="utf-16"?><MyMessage>Teno</MyMessage>';

and this gives the error:

Msg 9402, Level 16, State 1, Line 2
XML parsing: line 1, character 39, unable to switch the encoding

And the really, very simple fix is to:

UPDATE Customers 
SET data = N'<?xml version="1.0" encoding="utf-16"?><MyMessage>Teno</MyMessage>';

The difference is prefixing the Unicode string with N:

N'<?xml version="1.0" encoding="utf-16"?>Teno</MyMessage>'

In the former case, an unprefixed string is assumed to be varchar (e.g. Windows-1252 code-page). When it encounters the encoding="utf-16" inside the string, there is a conflict (and rightly so, since the string isn't utf-16).

The fix is to pass the string to SQL server as an nvarchar (i.e. UTF-16):

N'<?xml version="1.0" encoding="utf-16"?>'

That way the string is UTF-16, which matches the utf-16 encoding that the XML says it is. The carpet matches the curtains, so to speak.