我无法打印richTextBox.Text，因为它是多行的文本文件

using System.Drawing;
using System.Drawing.Printing;
using System.Windows.Forms;

public class PrintHelper
{
    private PrintDocument printDocument;
    private string textToPrint;

    public PrintHelper(string text)
    {
        printDocument = new PrintDocument();
        printDocument.PrintPage += new PrintPageEventHandler(PrintPage);
        textToPrint = text;
    }

    public void Print()
    {
        PrintDialog printDialog = new PrintDialog();
        printDialog.Document = printDocument;

        if (printDialog.ShowDialog() == DialogResult.OK)
        {
            printDocument.Print();
        }
    }

    private void PrintPage(object sender, PrintPageEventArgs e)
    {
        Font font = new Font("Arial", 12);
        Brush brush = new SolidBrush(Color.Black);
        float lineHeight = font.GetHeight(e.Graphics);
        float x = e.MarginBounds.Left;
        float y = e.MarginBounds.Top;

        while (textToPrint.Length > 0)
        {
            int charactersFitted, linesFilled;
            e.Graphics.MeasureString(textToPrint, font, e.MarginBounds.Size, StringFormat.GenericTypographic, out charactersFitted, out linesFilled);

            e.Graphics.DrawString(textToPrint.Substring(0, charactersFitted), font, brush, x, y);

            textToPrint = textToPrint.Substring(charactersFitted);

            y += lineHeight;
        }
    }
}

PrintHelper printHelper = new PrintHelper(richTextBox.Text);
printHelper.Print();