Wpf (c#) Printing Code for POS Printer

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C#

WPF

I have developed a project on retail management system. I have used POS Printer and
I don't know a code use for print bill using POS Printer using WPF (C#) Technology.
Please give me idea how it done.

// Print Event
		private void miPrint_Click(object sender, System.EventArgs e)
		{
			if (printDialog1.ShowDialog() == DialogResult.OK)
			{
               // printDocument1.DefaultPageSettings.PaperSize.Width = 9000;
				printDocument1.Print();
			}
		}
		
		// OnBeginPrint 
		private void OnBeginPrint(object sender, System.Drawing.Printing.PrintEventArgs e)
		{
			char[] param = {'\n'};
            PrinterSettings p = new PrinterSettings();
            PaperSize ps = new PaperSize ("Custom",9000,90000);
            printDocument1.DefaultPageSettings.PaperSize = ps;

			if (printDialog1.PrinterSettings.PrintRange == PrintRange.Selection)
			{
				lines = richTextBox1.SelectedText.Split(param);
			}
			else
			{
				lines = richTextBox1.Text.Split(param);
			}
			
			int i = 0;
			char[] trimParam = {'\r'};
			foreach (string s in lines)
			{
				lines[i++] = s.TrimEnd(trimParam);
			}
		}
        // OnPrintPage
		private void OnPrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
		{
			int x = e.MarginBounds.Left;
			int y = e.MarginBounds.Top;
			Brush brush = new SolidBrush(richTextBox1.ForeColor);
			
			while (linesPrinted < lines.Length)
			{
				e.Graphics.DrawString (lines[linesPrinted++],
					richTextBox1.Font, brush, x, y);
				y += 15;
				if (y >= e.MarginBounds.Bottom)
				{
					e.HasMorePages = true;
					return;
				}
			}
			
			linesPrinted = 0;
			e.HasMorePages = false;
		}
        // Page Setup
		private void miSetup_Click(object sender, System.EventArgs e)
		{
			// Call Dialog Box
			pageSetupDialog1.ShowDialog();
		}
        // Print Preview
		private void miPreview_Click(object sender, System.EventArgs e)
		{
			// Call Dialog Box
			printPreviewDialog1.ShowDialog();
		}

Thanks in advance.....