文本编辑器

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace SimpleEditor
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            string filename = null;
            if (args.Length != 0)
            {
                filename = args[0];
            }
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new SimpleEditorForm(filename));
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Drawing.Printing;

namespace SimpleEditor
{
    /// <summary>
    /// 文本编辑器
    /// 新建，编辑，保存，打印等功能
    /// </summary>
    public partial class SimpleEditorForm : Form
    {
        /// <summary>
        /// 文件名
        /// </summary>
        private string filename = "Untitled";

        private string[] lines;

        private int linesPrinted;

        /// <summary>
        /// 构造函数
        /// </summary>
        public SimpleEditorForm(string filename)
        {
            InitializeComponent();
            if (filename != null)
            {
                this.filename = filename;
                OpenFile();
            }
        }

        /// <summary>
        /// 新建
        /// </summary>
        private void OnFileNew(object sender, EventArgs e)
        {
            filename = "Untitled";
            SetFormTitle();
            txtEdit.Clear();
        }

        /// <summary>
        /// 打开
        /// </summary>
        private void OnFileOpen(object sender, EventArgs e)
        {
            if (dlgOpenFile.ShowDialog() == DialogResult.OK)
            {
                filename = dlgOpenFile.FileName;
                SetFormTitle();
                OpenFile();
            }
        }

        /// <summary>
        /// 保存
        /// </summary>
        private void OnFileSave(object sender, EventArgs e)
        {
            if (filename == "Untitled")
            {
                OnFileSaveAs(sender, e);
            }
            else
            {
                SaveFile();
            }
        }

        /// <summary>
        /// 另存为
        /// </summary>
        private void OnFileSaveAs(object sender, EventArgs e)
        {
            if (dlgSaveFile.ShowDialog() == DialogResult.OK)
            {
                filename = dlgSaveFile.FileName;
                SetFormTitle();
                SaveFile();
            }
        }

        /// <summary>
        /// 打开文件
        /// </summary>
        protected void OpenFile()
        {
            try
            {
                txtEdit.Clear();
                txtEdit.Text = File.ReadAllText(filename);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Simple Editor", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            }
        }

        /// <summary>
        /// 保存文件
        /// </summary>
        protected void SaveFile()
        {
            try
            {
                File.WriteAllText(filename, txtEdit.Text);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Simple Editor", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            }
        }

        /// <summary>
        /// 设置窗体标题
        /// </summary>
        private void SetFormTitle()
        {
            FileInfo fileInfo = new FileInfo(filename);// FileInfo 帮助获取文件名
            this.Text = fileInfo.Name + " - Simple Editor";
        }

        /// <summary>
        /// 打印
        /// </summary>
        private void OnFilePrint(object sender, EventArgs e)
        {
            try
            {
                if (txtEdit.SelectedText != null) // 只有在选中了一些文本后才设置改属性为 True
                {
                    dlgPrint.AllowSelection = true;// AllowSelection 属性设置了是否启用 "选中" 选项
                }
                if (dlgPrint.ShowDialog() == DialogResult.OK)
                {
                    printDocument.Print(); // 此方法在 PrintController 类的帮助下会触发 PrintPage 事件
                }
            }
            catch (InvalidPrinterException ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        /// <summary>
        /// 打印预览
        /// </summary>
        private void OnFilePrintPreview(object sender, EventArgs e)
        {
            dlgPrintPreview.ShowDialog();
        }

        /// <summary>
        /// 页面设置
        /// </summary>
        private void OnFilePageSetup(object sender, EventArgs e)
        {
            dlgPageSetup.ShowDialog();
        }

        /// <summary>
        /// 退出
        /// </summary>
        private void OnFileExit(object sender, EventArgs e)
        {

        }

        /// <summary>
        /// PrintPage事件 对于要打印的每一页都会发生一次
        /// </summary>
        private void OnPrintPage(object sender, PrintPageEventArgs e)
        {
            int x = e.MarginBounds.Left;
            int y = e.MarginBounds.Top;

            while (linesPrinted < lines.Length)
            {
                e.Graphics.DrawString(lines[linesPrinted++], new Font("Arial", 10), Brushes.Black, x, y);
                y += 15;
                if (y > e.PageBounds.Height - 80) // 减去 80 是控制不需要真正打印到页面的底部
                {
                    // 设置 true，通知控制器还有下一页，打印没有结束
                    // 这里将会再次调用 OnPrintPage() ，因此 x，y 的值会被重置
                    // 而 linesPrinted 则是成员变量，会保持先前已记录的打印行数
                    e.HasMorePages = true;
                    return;
                }
            }

            linesPrinted = 0;
            e.HasMorePages = false;
        }

        /// <summary>
        /// 打印之前，每一次打印任务只会发生一次
        /// </summary>
        private void OnBeginPrint(object sender, PrintEventArgs e)
        {
            char[] param = { '\n' };
            if (dlgPrint.PrinterSettings.PrintRange == PrintRange.Selection)
            {
                lines = txtEdit.SelectedText.Split(param);
            }
            else
            {
                lines = txtEdit.Text.Split(param);
            }
            int i = 0;
            char[] trimParam = { '\r' };
            foreach (string s in lines)
            {
                lines[i++] = s.TrimEnd(trimParam);
            }
        }

        /// <summary>
        /// 打印结束，主动释放一下资源让垃圾回收机制尽快回收
        /// </summary>
        private void OnEndPrint(object sender, PrintEventArgs e)
        {
            lines = null;
        }
    }
}