C# 读取、写入文件

读取文件

File.ReadAllText(textBox1.Text,Encoding.ASCII);

Form

namespace ReadWriteText
{
    public partial class Form1 : Form
    {
        private readonly OpenFileDialog chooseOpenFileDialog = new OpenFileDialog();
        private string chosenFile;

        public Form1()
        {
            InitializeComponent();

            menuFileOpen.Click += OnFileOpen;
            chooseOpenFileDialog.FileOk += OnOpenFileDialogOK;

            menuFileSave.Click += OnFileSave;
        }

        private void OnFileOpen(object Sender, EventArgs e)
        {
            chooseOpenFileDialog.ShowDialog();
        }

        private void OnFileSave(object Sender, EventArgs e)
        {
            SaveFile();
        }

        private void OnOpenFileDialogOK(object Sender, CancelEventArgs e)
        {
            chosenFile = chooseOpenFileDialog.FileName;
            Text = Path.GetFileName(chosenFile);
            DisplayFile();
        }

        private void SaveFile()
        {
            StreamWriter sw = new StreamWriter(chosenFile, false,
                                               Encoding.Unicode);
            foreach (string line in textBoxContents.Lines)
                sw.WriteLine(line);
            sw.Close();
        }

        private void DisplayFile()
        {
            StringCollection linesCollection = ReadFileIntoStringCollection();
            string[] linesArray = new string[linesCollection.Count];
            linesCollection.CopyTo(linesArray, 0);
            textBoxContents.Lines = linesArray;
        }

        private StringCollection ReadFileIntoStringCollection()
        {
            const int MaxBytes = 65536;
            StreamReader sr = new StreamReader(chosenFile);
            StringCollection result = new StringCollection();
            int nBytesRead = 0;
            string nextLine;
            while ((nextLine = sr.ReadLine()) != null)
            {
                nBytesRead += nextLine.Length;
                if (nBytesRead > MaxBytes)
                    break;
                result.Add(nextLine);
            }
            sr.Close();
            return result;
        }
    }
}

Designer

namespace ReadWriteText
{
    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.components = new System.ComponentModel.Container();
            this.menuFileOpen = new System.Windows.Forms.MenuItem();
            this.textBoxContents = new System.Windows.Forms.TextBox();
            this.menuItem1 = new System.Windows.Forms.MenuItem();
            this.menuFileSave = new System.Windows.Forms.MenuItem();
            this.mainMenu1 = new System.Windows.Forms.MainMenu(this.components);
            this.SuspendLayout();
            // 
            // menuFileOpen
            // 
            this.menuFileOpen.Index = 0;
            this.menuFileOpen.Text = "&Open";
            // 
            // textBoxContents
            // 
            this.textBoxContents.Dock = System.Windows.Forms.DockStyle.Fill;
            this.textBoxContents.Font = new System.Drawing.Font("Courier New", 9F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.textBoxContents.Location = new System.Drawing.Point(0, 0);
            this.textBoxContents.Multiline = true;
            this.textBoxContents.Name = "textBoxContents";
            this.textBoxContents.ScrollBars = System.Windows.Forms.ScrollBars.Both;
            this.textBoxContents.Size = new System.Drawing.Size(284, 245);
            this.textBoxContents.TabIndex = 1;
            // 
            // menuItem1
            // 
            this.menuItem1.Index = 0;
            this.menuItem1.MenuItems.AddRange(new System.Windows.Forms.MenuItem[] {
            this.menuFileOpen,
            this.menuFileSave});
            this.menuItem1.Text = "&File";
            // 
            // menuFileSave
            // 
            this.menuFileSave.Index = 1;
            this.menuFileSave.Text = "&Save";
            // 
            // mainMenu1
            // 
            this.mainMenu1.MenuItems.AddRange(new System.Windows.Forms.MenuItem[] {
            this.menuItem1});
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(284, 245);
            this.Controls.Add(this.textBoxContents);
            this.Menu = this.mainMenu1;
            this.Name = "Form1";
            this.Text = "Form1";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.MenuItem menuFileOpen;
        private System.Windows.Forms.TextBox textBoxContents;
        private System.Windows.Forms.MenuItem menuItem1;
        private System.Windows.Forms.MenuItem menuFileSave;
        private System.Windows.Forms.MainMenu mainMenu1;
    }
}