C# printing in dot matrix printer

public void ReadFile()
        {
            documentContents = File.ReadAllText(FilePath);
            stringToPrint = documentContents;
        }
        private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
        {

            int charactersOnPage = 0;
            int linesPerPage = 0;

           
            e.Graphics.MeasureString(stringToPrint, this.Font,
                e.MarginBounds.Size, StringFormat.GenericTypographic,
                out charactersOnPage, out linesPerPage);

           
            e.Graphics.DrawString(stringToPrint, this.Font, Brushes.Black,
           110,10);

           
            stringToPrint = stringToPrint.Substring(charactersOnPage);

            
            e.HasMorePages = (stringToPrint.Length > 0);

           
            if (!e.HasMorePages)
                stringToPrint = documentContents;
        }
        private void btnPreview_Click(object sender, EventArgs e)
        {
            ReadFile();

            printPreviewDialog1.Document = printDocument1;
            printPreviewDialog1.ShowDialog();
        }
    }