C# Oracleclient Updating NULL CLOB

In the Oracle database, the column that I would like to update is designated as a CLOB. I am using C# and the Oracle Instant Client (System.Data.OracleClient) to interface.

The code shown below works perfectly if the CLOB column already has data inside it when I update. However, if prior to the update the column is NULL, it throws the error:

Null LOBs may not be modified. (I received this error before wrapping the .Erase and .SetLength in the .Null conditional).

OR

Invalid operation. The connection is closed.

To limit changes at the database level, I don't want to use a proc (although I know it's probably best!).

What am I missing? What needs done if the column is NULL previous to the update?

Thanks!
Chuck

private void UpdateCaseNotes(string SchemaReference, string DefectId, string Comments)
    {
      string connectionstring = ConfigurationSettings.AppSettings["DBConnStr"];
      string sql = "SELECT " + colCaseComment + " FROM " + SchemaReference + ".BUG WHERE BG_BUG_ID=" + DefectId + " FOR UPDATE";
      
      using (OracleConnection conn = new OracleConnection(connectionstring))
      {
        using (OracleCommand cmd = new OracleCommand(sql, conn))
        {
          conn.Open();
          using (OracleDataReader dr = cmd.ExecuteReader())
          {
            OracleTransaction tx = conn.BeginTransaction();
            
            cmd.Transaction = tx;
            dr.Read();
 
            byte[] clobByte = Encoding.Unicode.GetBytes(Comments);
            OracleLob clobColumn = dr.GetOracleLob(0);
            
            Logger.Write(conn.State.ToString() + " - Connection State - " + clobByte.Length, "Tracing");
 
            clobColumn.BeginBatch(OracleLobOpenMode.ReadWrite);
            
            if(clobColumn != OracleLob.Null)
            {
              clobColumn.Erase(0, clobColumn.Length);
              clobColumn.SetLength(0); 
            }
            
            clobColumn.Write(clobByte, 0, clobByte.Length);
            clobColumn.EndBatch();
            
            tx.Commit();
          }
          if (conn.State.ToString().Equals("Open"))
          {
            conn.Close();
          }
        }
      }
    }

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