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, );
             textBoxContents.Lines = linesArray;
         }

         private StringCollection ReadFileIntoStringCollection()
         {
             const int MaxBytes = ;
             StreamReader sr = new StreamReader(chosenFile);
             StringCollection result = new StringCollection();
             int nBytesRead = ;
             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 = ;
             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)()));
             this.textBoxContents.Location = new System.Drawing.Point(, );
             this.textBoxContents.Multiline = true;
             this.textBoxContents.Name = "textBoxContents";
             this.textBoxContents.ScrollBars = System.Windows.Forms.ScrollBars.Both;
             this.textBoxContents.Size = new System.Drawing.Size(, );
             this.textBoxContents.TabIndex = ;
             //
             // menuItem1
             //
             this.menuItem1.Index = ;
             this.menuItem1.MenuItems.AddRange(new System.Windows.Forms.MenuItem[] {
             this.menuFileOpen,
             this.menuFileSave});
             this.menuItem1.Text = "&File";
             //
             // menuFileSave
             //
             this.menuFileSave.Index = ;
             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(, );
             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;
     }
 }