.NET: How to insert XML document into SQL Server

Question

I want to insert arbitrary XML into SQL Server. The XML is contained in an XmlDocument object.

The column I want to insert into is either nvarchar, ntext, or xml column (If it makes your life easier then you can pick which type it is. Really it's an xml column.)

Prototype

void SaveXmlToDatabase(DbConnection connection,
      XmlDocument xmlToSave,
      String tableName, String columnName);
{

}

The reason I ask is because I'm trying to find the proper way to turn the XmlDocument into something the database can take - being sure to keep the encodings right:

• I have to make sure the encoding using during insert matches what the database takes
• I have to synchronize the <?xml version="1.0" encoding="windows-1252"?> element

I know ntext, nvarchar, or xml are stored as UTF-16 inside SQL Server. So I have to be sure to give the data to SQL Server as UTF-16. This isn't a problem for Strings in .NET, since they are unicode UTF-16.

The 2nd problem, synchronizing the encoding attribute, is a tougher nut to crack. I have to figure out how to find the declaration element through the XmlDocument object:

<?xml version="1.0" encoding="windows-1252"?>   (or whatever the encoding may be)

and adjust it to UTF-16

<?xml version="1.0" encoding="UTF-16"?>

---

My naive attempt (that fails)

Ignoring the encoding in the XML declaration, and just figuring out how to save anything into SQL Server:

void SaveXmlToDatabase(DbConnection connection,
      XmlDocument xmlToSave,
      String tableName, String columnName);
{
   String sql = "INSERT INTO "+tableName+" ("+columnName+") 
          VALUES ('"+xmlToSave.ToString()+"')";

   using (DbCommand command = connection.CreateCommand())
   {
      command.CommandText = sql;

      DbTransaction trans = connection.BeginTransaction();
      try
      {
         command.ExecuteNonQuery();
         trans.Commit();
      }
      catch (Exception)
      {
         trans.Rollback();
         throw;
      }
   }
}

This fails because the sql I try to run is:

INSERT INTO LiveData (RawXML) 
VALUES ('System.Xml.XmlDocument')

This is because XmlDocument.ToString() returns "System.Xml.XmlDocument". Peeking at the implementation, it see that it literally is calling:

this.GetType().ToString();

Aside: Microsoft seems to have gone out of their way to prevent you from getting the Xml as a string - presumably because it leads to bugs (But they don't tell us what bugs, why they're bugs, or the right way to convert an XmlDocument into a String!)

See also

• C#/SQL - What’s wrong with SqlDbType.Xml in procedures ?
• How to convert XmlDocument to XmlReader for SqlXml data type.

Answer 1

You have to use an SqlParameter. I would recommend doing it like that:

command.Parameters.Add(
   new SqlParameter("@xml", SqlDbType.Xml) 
       {Value = new SqlXml(new XmlTextReader(xmlToSave.InnerXml
                       , XmlNodeType.Document, null)) })

and the SQL should look like:

String sql = "INSERT INTO "+tableName+" ("+columnName+") VALUES (@xml)";

And since the first child is always the xml node, you can replace the encoding with the following statement.

xmlToSave.FirstChild.InnerText = "version=\"1.0\" encoding=\"UTF-16\"";

All in all it would look like that:

void SaveXmlToDatabase(DbConnection connection,
      XmlDocument xmlToSave,
      String tableName, String columnName);
{
   String sql = "INSERT INTO "+tableName+" ("+columnName+") VALUES (@xml)";

   using (DbCommand command = connection.CreateCommand())
   {
      xmlToSave.FirstChild.InnerText = "version=\"1.0\" encoding=\"UTF-16\"";             
      command.CommandText = sql;
      command.Parameters.Add(
        new SqlParameter("@xml", SqlDbType.Xml) 
           {Value = new SqlXml(new XmlTextReader(xmlToSave.InnerXml
                       , XmlNodeType.Document, null)) });


      DbTransaction trans = connection.BeginTransaction();
      try
      {
         command.ExecuteNonQuery();
         trans.Commit();
      }
      catch (Exception)
      {
         trans.Rollback();
         throw;
      }
   }
}

Answer 2

The simplest solution is to use the OuterXml attribute of the document. I came across your question while trying to solve the problem under the condition that I could not executed a stored procedure. OuterXml returns the string of text you were expecting to get from .Value or .ToString()

void SaveXmlToDatabase(DbConnection connection, 
      XmlDocument xmlToSave, 
      String tableName, String columnName); 
{ 
   String sql = "INSERT INTO "+tableName+" ("+columnName+")  
          VALUES ('"+xmlToSave.OuterXml+"')"; 

   using (DbCommand command = connection.CreateCommand()) 
   { 
      command.CommandText = sql; 

      DbTransaction trans = connection.BeginTransaction(); 
      try 
      { 
         command.ExecuteNonQuery(); 
         trans.Commit(); 
      } 
      catch (Exception) 
      { 
         trans.Rollback(); 
         throw; 
      } 
   } 
} 

Answer 3

Better late than never... I think you're looking for something like this:

void SaveXmlToDatabase(DbConnection connection,
      XmlDocument xmlToSave,
      String tableName, String columnName)
{
   String sql = "INSERT INTO "+tableName+" ("+columnName+") 
          VALUES (@XmlVal)";

   using (DbCommand command = connection.CreateCommand())
   {
      command.CommandText = sql;
      command.Parameters.AddWithValue("XmlVal", new SqlXml(new XmlNodeReader(xmlToSave)));

      DbTransaction trans = connection.BeginTransaction();
      try
      {
         command.ExecuteNonQuery();
         trans.Commit();
      }
      catch (Exception)
      {
         trans.Rollback();
         throw;
      }
   }
}

The XmlNodeReader object traverses and properly encodes the XmlDocument (or any other XmlNode), and the SqlXml object encapsulates that into the SqlDbType suitable for use with the parameter. This is safer and probably more efficient than using a string intermediary.

Answer 4

Just wanted to add an SQLConnection equivalent to Jonathan Overholt's solution:

private void StoreXMLInDatabase(XmlDocument doc)
{
    // xmlvalue is the name of the database column you want to insert into
    String sql = "INSERT INTO [tablename] (xmlvalue) VALUES (@xmlvalue)";
    // In order to read out you connection string from app.config, remember first to add a reference to System.Configuration in references,
    // and set using System.Configuration; in the top of the file
    string connString = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;  
    using (SqlConnection conn = new SqlConnection(connString))
    {
        if (conn.State == ConnectionState.Closed)
        {
            conn.Open();
        }
        SqlTransaction transaction = conn.BeginTransaction();
        try
        {
            // Remember to specify the SqlTransaction *name* (transaction)
            SqlCommand cobj = new SqlCommand(sql, conn, transaction);
            cobj.CommandText = sql;
            cobj.Parameters.AddWithValue("xmlvalue", new SqlXml(new XmlNodeReader(doc)));
            cobj.ExecuteNonQuery();
            transaction.Commit();
        }
        catch (SqlException ex)
        {
            //2627 = inserting duplicate key fail. Lets the procedure continue although an identity insert fail occurs
            if (ex.Number == 2627)
            {
                transaction.Rollback();
            }
        }
    } // end using
}

Tested OK in Visual studio 2017 and 2013 with .net up to version 4.6.2, and against MS SQL Server 2008 R2, 2012 and 2016

If an identity insert fail and you want to stop the procedure then, just insert a line after transaction.Rollback() like this:

throw;

Or you can stop the procedure in any circumstance by putting the transaction.Rollback(); and throw; lines just outside the conditional (the if)