C#

Hello Every Body!
I just try to text analysis program by C# .In the program i uses RichTextEdit . I want to load word file, text file , pdf to Richtext Edit Box.  Now i can load these file to RichText Edit . But i can't change font these text. Just i used  Microsoft.Office.Interop.Word; . Check my code below. Thanks for your kindness! 
 
 
 
public void ReadMsWord()
{
// variable to store file path
string filePath=null;
// open dialog box to select file
OpenFileDialog file= new OpenFileDialog();
// dilog box title name
file.Title="Word File";
// set initial directory of computer system
file.InitialDirectory= "c:\\";
// set restore directory
file.RestoreDirectory= true;
// execute if block when dialog result box click ok button
if (file.ShowDialog() ==DialogResult.OK)
{
// store selected file path
filePath=file.FileName.ToString();
}
try
{
// create word application
Microsoft.Office.Interop.Word.Application word =new Microsoft.Office.Interop.Word.Application();
// create object of missing value
object miss= System.Reflection.Missing.Value;
// create object of selected file path
object path=filePath;
// set file path mode
object readOnly= false;
//Microsoft.Office.Interop.Word.Font f = new Microsoft.Office.Interop.Word.Font();
//f.Name = "Zawgyi-One, 8.25pt";
//object fo = f;
// open document
Microsoft.Office.Interop.Word.Document docs=word.Documents.Open(ref path, ref miss, ref readOnly, ref miss, ref miss, ref miss, ref miss, ref miss,ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss, ref miss);
// select whole data from active window document
docs.ActiveWindow.Selection.WholeStory();
// handover the data to cllipboard
docs.ActiveWindow.Selection.Copy();
// clipboard create reference of idataobject interface which transfer the data
IDataObject data= Clipboard.GetDataObject();
//Microsoft.Office.Interop.Word.Range rng = docs.Paragraphs[1].Range;
//rng.Font.Name = "Zawgyi-One";
//set data into richtextbox control in text format
richTextBox1.Text=data.GetData(DataFormats.Text).ToString();
//word.Selection.Font.Name = "Zawgyi-One";
// Microsoft.Office.Interop.Word.Document document = new Microsoft.Office.Interop.Word.Document();
// this.richTextBox1.SelectAll();
//System.Drawing.Font currentFont = richTextBox1.SelectionFont;
// richTextBox1.SelectionFont = new System.Drawing.Font(currentFont.FontFamily,currentFont.Size,newFontStyle);
// read bitmap image from clipboard with help of iddataobject interface
Image img= (Image)data.GetData(DataFormats.Bitmap);
// close the document
docs.Close(ref miss, ref miss, ref miss);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}

   static class GMLogger
    {

       private static List<string> _buffer = new List<string>();
       private static int _maxBufferSize = 25;  // number of messages  permitted in the buffer at a time
       public static string _logDir = "C:\\Logs";
       private static readonly object _syncObject = new object();

       // Log message
        public static  void Log(string logMessage)
        {
            try
            {
                lock (_syncObject)
                {
                    _buffer.Add(logMessage);

                    Save(_buffer);
                }
            }
            catch (Exception ex)
            {
                throw;
            }
        }

       // Save buffer if needed
        private static void Save(List<string> buffer)
        {
            if (buffer.Count > _maxBufferSize)
            {
                // Write to file
                if (!_logDir.EndsWith("\\")) _logDir += "\\"; 
                DirectoryInfo di = Directory.CreateDirectory(_logDir);
                var todaysLogFilePath = Path.Combine(_logDir,
                                                       ("Log" + DateTime.Now.ToString("yyyy-MMMM-dd") + ".txt"));
                using (FileStream aFile = new FileStream(todaysLogFilePath, FileMode.Append, FileAccess.Write, FileShare.None))
                using (StreamWriter sw = new StreamWriter(aFile))
                {
                    for (int i = 0; i < buffer.Count(); i++)
                    {
                        sw.WriteLine(buffer[i]);
                    }
                }

                // Clear buffer
                buffer.Clear();
            }



    }
}