context: // Copyright (c) 2004-2008 MySQL AB, 2008-2009 Sun Microsystems, Inc.
  //
  // MySQL Connector/NET is licensed under the terms of the GPLv2
  // <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most 
  // MySQL Connectors. There are special exceptions to the terms and 
  // conditions of the GPLv2 as it is applied to this software, see the 
  // FLOSS License Exception
  // <http://www.mysql.com/about/legal/licensing/foss-exception.html>.
  //
  // This program is free software; you can redistribute it and/or modify 
  // it under the terms of the GNU General Public License as published 
  // by the Free Software Foundation; version 2 of the License.
  //
  // This program is distributed in the hope that it will be useful, but 
  // WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
  // or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
  // for more details.
  //
  // You should have received a copy of the GNU General Public License along 
  // with this program; if not, write to the Free Software Foundation, Inc., 
  // 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
  
  using System;
  using System.Data;
  using MySql.Data.MySqlClient;
  using MySql.Data.MySqlClient.Properties;
  
  namespace MySql.Data.Types
  {
  
    internal struct MySqlGuid : IMySqlValue
    {
      Guid mValue;
      private bool isNull;
      private byte[] bytes;
      private bool oldGuids;
  
      public MySqlGuid(byte[] buff)
      {
        oldGuids = false;
        mValue = new Guid(buff);
        isNull = false;
        bytes = buff;
      }
  
      public byte[] Bytes
      {
        get { return bytes; }
      }
  
      public bool OldGuids
      {
        get { return oldGuids; }
        set { oldGuids = value; }
      }
  
      #region IMySqlValue Members
  
      public bool IsNull
      {
        get { return isNull; }
      }
  
      MySqlDbType IMySqlValue.MySqlDbType
      {
        get { return MySqlDbType.Guid; }
      }
  
      object IMySqlValue.Value
      {
        get { return mValue; }
      }
  
      public Guid Value
      {
        get { return mValue; }
      }
  
      Type IMySqlValue.SystemType
      {
        get { return typeof(Guid); }
      }
  
      string IMySqlValue.MySqlTypeName
      {
        get { return OldGuids ? "BINARY(16)" : "CHAR(36)"; }
      }
  
      void IMySqlValue.WriteValue(MySqlPacket packet, bool binary, object val, int length)
      {
        Guid guid = Guid.Empty;
        string valAsString = val as string;
        byte[] valAsByte = val as byte[];
  
        if (val is Guid)
          guid = (Guid)val;
        else
        {
          try
          {
            if (valAsString != null)
              guid = new Guid(valAsString);
            else if (valAsByte != null)
              guid = new Guid(valAsByte);
          }
          catch (Exception ex)
          {
            throw new MySqlException(Resources.DataNotInSupportedFormat, ex);
          }
        }
  
        if (OldGuids)
          WriteOldGuid(packet, guid, binary);
        else
        {
          guid.ToString("D");
  
          if (binary)
            packet.WriteLenString(guid.ToString("D"));
          else
            packet.WriteStringNoNull("'" + MySqlHelper.EscapeString(guid.ToString("D")) + "'");
        }
      }
  
      private void WriteOldGuid(MySqlPacket packet, Guid guid, bool binary)
      {
        byte[] bytes = guid.ToByteArray();
  
        if (binary)
        {
          packet.WriteLength(bytes.Length);
          packet.Write(bytes);
        }
        else
        {
          packet.WriteStringNoNull("_binary ");
          packet.WriteByte((byte)'\'');
          EscapeByteArray(bytes, bytes.Length, packet);
          packet.WriteByte((byte)'\'');
        }
      }
  
      private static void EscapeByteArray(byte[] bytes, int length, MySqlPacket packet)
      {
        for (int x = 0; x < length; x++)
        {
          byte b = bytes[x];
          if (b == '\0')
          {
            packet.WriteByte((byte)'\\');
            packet.WriteByte((byte)'0');
          }
  
          else if (b == '\\' || b == '\'' || b == '\"')
          {
            packet.WriteByte((byte)'\\');
            packet.WriteByte(b);
          }
          else
            packet.WriteByte(b);
        }
      }
  
      private MySqlGuid ReadOldGuid(MySqlPacket packet, long length)
      {
        if (length == -1)
          length = (long)packet.ReadFieldLength();
  
        byte[] buff = new byte[length];
        packet.Read(buff, 0, (int)length);
        MySqlGuid g = new MySqlGuid(buff);
        g.OldGuids = OldGuids;
        return g;
      }
  
      IMySqlValue IMySqlValue.ReadValue(MySqlPacket packet, long length, bool nullVal)
      {
        MySqlGuid g = new MySqlGuid();
        g.isNull = true;
        g.OldGuids = OldGuids;
        if (!nullVal)
        {
          if (OldGuids)
            return ReadOldGuid(packet, length);
          string s = String.Empty;
          if (length == -1)
            s = packet.ReadLenString();
          else
            s = packet.ReadString(length);
          g.mValue = new Guid(s);
          g.isNull = false;
        }
        return g;
      }
  
      void IMySqlValue.SkipValue(MySqlPacket packet)
      {
        int len = (int)packet.ReadFieldLength();
        packet.Position += len;
      }
  
      #endregion
  
      public static void SetDSInfo(MySqlSchemaCollection sc)
      {
        // we use name indexing because this method will only be called
        // when GetSchema is called for the DataSourceInformation 
        // collection and then it wil be cached.
        MySqlSchemaRow row = sc.AddRow();
        row["TypeName"] = "GUID";
        row["ProviderDbType"] = MySqlDbType.Guid;
        row["ColumnSize"] = 0;
        row["CreateFormat"] = "BINARY(16)";
        row["CreateParameters"] = null;
  
gt:       row["DataType"] = "System.Guid";