Displaying Greek letters in .NET using char casting

string attachment = "attachment; filename=download.xls";
                Response.ClearContent();
                Response.AddHeader("content-disposition", attachment);
                Response.ContentType = "application/vnd.xls";

                //Response.BinaryWrite(UTF8Encoding.UTF8.GetBytes(attachment)); 

                Response.Charset = UnicodeEncoding.UTF8.WebName;
                Response.HeaderEncoding = UnicodeEncoding.UTF8;
                Response.ContentEncoding = UnicodeEncoding.UTF8;

                string tab = " ";
                foreach (DataColumn dc in dt.Columns)
                {
                    Response.Write(tab + dc.ColumnName);
                    tab = "\t";
                }
                Response.Write("\n");
                int i;
             
                UTF8Encoding utf8 = new UTF8Encoding();
                foreach (DataRow dr in dt.Rows)
                {
                   
                    tab = "";
                    for (i = 0; i < dt.Columns.Count - 1; i++)
                    {
                     
                        Console.WriteLine(dr[i].ToString());
                        tab = "\t";
                    }
                    Response.Write("\n");

                }
                Response.End();

<pre>

char theta = '\u0398';
char omega = '\u03A9';