C# 文本文件打印類庫(C#)

我寫了一個打印文本文件的類庫，功能包括：打印預覽、打印。打印時可以選擇打印機，可以指定頁碼范圍。調用方法非常簡單：
TextFilePrinter p = new TextFilePrinter(tbxFileName.Text);
p.View(); // 打印預覽
p.Print(); // 打印文件
使用 TextFilePrinter 類的以下構造函數可以指定打印時使用的字體：
TextFilePrinter(string fileName, Encoding theEncode, Font theFont)
下面測試程序運行時的截圖:

點擊“預覽”按鈕后：

點擊“打印”按鈕后：

這幅圖中的打印機：“Microsoft Office Doument Image Writer”是 Microsoft Office 2003 軟件提供一個虛擬打印機，用來調試打印程序非常方便(使用“打印預覽”也可以調試打印程序，但“打印預覽”只能使用默認的打印機和默認的打印屬性，也不能設置頁碼范圍)，可以設置打印屬性和頁碼范圍以及打印份數。使用它來調試打印程序，可以節省不少打印紙。為建設節約型社會作貢獻 :)

這幅圖就是該虛擬打印機在屏幕上的顯示的結果。
這里是測試程序的源代碼：

// PrintFile.cs - 文件打印程序
// 編譯方法: csc /t:winexe PrintFile.cs TextFilePrinter.cs

using System;
using System.Drawing;
using System.Windows.Forms;
using Skyiv.Util;

namespace Skyiv.Ben.Test
{
  class PrintFileForm : Form
  {
    TextBox tbxFileName;
    
    public PrintFileForm()
    {
      SuspendLayout();
      
      Button btnFileName = new Button();
      btnFileName.Text = "文件名";
      btnFileName.Location = new Point(10, 10);
      btnFileName.Size = new Size(60, 24);
      btnFileName.Click += new EventHandler(BtnFileName_Click);

      Button btnPrint = new Button();
      btnPrint.Text = "打印";
      btnPrint.Location = new Point(75, 10);
      btnPrint.Size = new Size(60, 24);
      btnPrint.Click += new EventHandler(BtnPrint_Click);

      Button btnView = new Button();
      btnView.Text = "預覽";
      btnView.Location = new Point(140, 10);
      btnView.Size = new Size(60, 24);
      btnView.Click += new EventHandler(BtnView_Click);

      tbxFileName = new TextBox();
      tbxFileName.Text = "PrintFile.cs";
      tbxFileName.Location = new Point(10, 44);
      tbxFileName.Size = new Size(190, 20);
      tbxFileName.ReadOnly = true;
      tbxFileName.Anchor = (AnchorStyles.Top | AnchorStyles.Left | AnchorStyles.Right);

      Controls.AddRange(new Control[]{btnFileName, btnPrint, btnView, tbxFileName});
      Text = "文本文件打印程序";
      ClientSize = new Size(210, 80);

      ResumeLayout(false);
    }
    
    void BtnFileName_Click(object sender, EventArgs e)
    {
      OpenFileDialog dlg = new OpenFileDialog();
      if(dlg.ShowDialog() != DialogResult.OK) return;
      tbxFileName.Text = dlg.FileName;
    }

    void BtnPrint_Click(object sender, EventArgs e)
    {
      TextFilePrinter p = new TextFilePrinter(tbxFileName.Text);
      p.Print();
    }
    
    void BtnView_Click(object sender, EventArgs e)
    {
      TextFilePrinter p = new TextFilePrinter(tbxFileName.Text);
      p.View();
    }
    
    static void Main()
    {
      Application.Run(new PrintFileForm());
    }
  }
}

這里是該類的源代碼:

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

namespace Skyiv.Util
{
  sealed class TextFilePrinter
  {
    string fileName;
    Encoding theEncode;
    Font theFont;
    StreamReader srToPrint;
    int currPage;

    public TextFilePrinter(string fileName)
      : this(fileName, Encoding.GetEncoding("GB18030"), new Font("新宋體", 10))
    {
    }

    public TextFilePrinter(string fileName, Encoding theEncode, Font theFont)
    {
      this.fileName = fileName;
      this.theEncode = theEncode;
      this.theFont = theFont;
    }

    public void Print()
    {
      using (srToPrint = new StreamReader(fileName, theEncode))
      {
        PrintDialog dlg = new PrintDialog();
        dlg.Document = GetPrintDocument();
        dlg.AllowSomePages = true;
        dlg.AllowPrintToFile = false;
        if (dlg.ShowDialog() == DialogResult.OK) dlg.Document.Print();
      }
    }

    public void View()
    {
      using (srToPrint = new StreamReader(fileName, theEncode))
      {
        PrintPreviewDialog dlg = new PrintPreviewDialog();
        dlg.Document = GetPrintDocument();
        dlg.ShowDialog();
      }
    }

    PrintDocument GetPrintDocument()
    {
      currPage = 1;
      PrintDocument doc = new PrintDocument();
      doc.DocumentName = fileName;
      doc.PrintPage += new PrintPageEventHandler(PrintPageEvent);
      return doc;
    }

    void PrintPageEvent(object sender, PrintPageEventArgs ev)
    {
      string line = null;
      float linesPerPage = ev.MarginBounds.Height / theFont.GetHeight(ev.Graphics);
      bool isSomePages = ev.PageSettings.PrinterSettings.PrintRange == PrintRange.SomePages;
      if (isSomePages)
      {
        while (currPage < ev.PageSettings.PrinterSettings.FromPage)
        {
          for (int count = 0; count < linesPerPage; count++)
          {
            line = srToPrint.ReadLine();
            if (line == null) break;
          }
          if (line == null) return;
          currPage++;
        }
        if (currPage > ev.PageSettings.PrinterSettings.ToPage) return;
      }
      for (int count = 0; count < linesPerPage; count++)
      {
        line = srToPrint.ReadLine();
        if (line == null) break;
        ev.Graphics.DrawString(line, theFont, Brushes.Black, ev.MarginBounds.Left,
          ev.MarginBounds.Top + (count * theFont.GetHeight(ev.Graphics)), new StringFormat());
      }
      currPage++;
      if (isSomePages && currPage > ev.PageSettings.PrinterSettings.ToPage) return;
      if (line != null) ev.HasMorePages = true;
    }
  }
}

這些程序都相當簡當明了，這里就不再解釋了。
這個類庫有個缺點：當文本文件中的一行不能在打印紙的一行中打印完時，該行的后半部就丟失了。