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存取文件
发布于:第八基地 来源:duote 作者:天堂路上 时间:2016-04-11 点击:259

  有时我们需要把一些大的数据对象如图片、可执行文件、视频和文档等数据存入数据库。在MS SQL Server中,这要用到Image数据类型,可以保存多达2G的数据。以下给出一个通过ADO.NET和MS SQL Server实现的小小的例子。

  先创建一个测试数据表。

  在查询分析器中输入并执行以下语句:

  Create table [imgtable](

  [imgid] [int] IDENTITY(1,1) NOT NULL,

  [imgname] [varchar](100) COLLATE Chinese_PRC_CI_AS NULL,

  [imgData] [image] NULL,

  PRIMARY KEY CLUSTERED

  (

  [imgid]

  ) ON [PRIMARY]

  ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

  这要在你所选的数据库中就多了一个名叫imgtable的表。

  VS中的代码如下:

  using System;

  using System.Drawing;

  using System.Collections;

  using System.ComponentModel;

  using System.Windows.Forms;

  using System.Data;

  using System.Data.SqlClient;

  using System.IO;

  namespace ADO_Demo

  {

  /// <summary>

  /// Form1 的摘要说明。

  /// </summary>

  public class ADO_Demo : System.Windows.Forms.Form

  {

  private System.Windows.Forms.Button button1;

  private System.Windows.Forms.Button button2;

  private System.Windows.Forms.PictureBox pictureBox1;

  private System.Windows.Forms.OpenFileDialog openFileDialog1;

  private System.Windows.Forms.Button button3;

  /// <summary>

  /// 必需的设计器变量。

  /// </summary>

  private System.ComponentModel.Container components = null;

  public ADO_Demo()

  {

  //

  // Windows 窗体设计器支持所必需的

  //

  InitializeComponent();

  //

  // TODO: 在 InitializeComponent 调用后添加任何构造函数代码

  //

  }

  /// <summary>

  /// 清理所有正在使用的资源。

  /// </summary>

  protected override void Dispose( bool disposing )

  {

  if( disposing )

  {

  if (components != null)

  {

  components.Dispose();

  }

  }

  base.Dispose( disposing );

  }
#region Windows 窗体设计器生成的代码

  /// <summary>

  /// 设计器支持所需的方法 - 不要使用代码编辑器修改

  /// 此方法的内容。

  /// </summary>

  private void InitializeComponent()

  {

  this.button1 = new System.Windows.Forms.Button();

  this.button2 = new System.Windows.Forms.Button();

  this.pictureBox1 = new System.Windows.Forms.PictureBox();

  this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();

  this.button3 = new System.Windows.Forms.Button();

  this.SuspendLayout();

  //

  // button1

  //

  this.button1.Location = new System.Drawing.Point(368, 48);

  this.button1.Name = "button1";

  this.button1.Size = new System.Drawing.Size(104, 23);

  this.button1.TabIndex = 0;

  this.button1.Text = "保存图片";

  this.button1.Click += new System.EventHandler(this.button1_Click);

  //

  // button2

  //

  this.button2.Location = new System.Drawing.Point(368, 120);

  this.button2.Name = "button2";

  this.button2.Size = new System.Drawing.Size(104, 23);

  this.button2.TabIndex = 1;

  this.button2.Text = "显示图片";

  this.button2.Click += new System.EventHandler(this.button2_Click);

  //

  // pictureBox1

  //

  this.pictureBox1.Location = new System.Drawing.Point(8, 16);

  this.pictureBox1.Name = "pictureBox1";

  this.pictureBox1.Size = new System.Drawing.Size(312, 288);

  this.pictureBox1.TabIndex = 2;

  this.pictureBox1.TabStop = false;

  //

  // openFileDialog1

  //

  this.openFileDialog1.FileOk += new System.ComponentModel.CancelEventHandler(this.openFileDialog1_FileOk);

  //

  // button3

  //

  this.button3.Location = new System.Drawing.Point(368, 200);

  this.button3.Name = "button3";

  this.button3.Size = new System.Drawing.Size(104, 23);

  this.button3.TabIndex = 1;

  this.button3.Text = "读取文件并打开";

  this.button3.Click += new System.EventHandler(this.button3_Click);

  //

  // ADO_Demo

  //

  this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);

  this.ClientSize = new System.Drawing.Size(496, 317);

  this.Controls.Add(this.pictureBox1);

  this.Controls.Add(this.button2);

  this.Controls.Add(this.button1);

  this.Controls.Add(this.button3);

  this.Name = "ADO_Demo";

  this.Text = "ADO_Demo";

  this.ResumeLayout(false);

  }

  #endregion

  /// <summary>

  /// 应用程序的主入口点。

  /// </summary>

  [STAThread]

  static void Main()

  {

  application.Run(new ADO_Demo());

  }

  /// <summary>

  /// 点击打开文件对话框确定按钮,将文件保存到数据库中

  /// </summary>

  /// <param name="sender"></param>

  /// <param name="e"></param>

  private void openFileDialog1_FileOk(object sender, System.ComponentModel.CancelEventArgs e)

  {

  string filename = this.openFileDialog1.FileName;

  SqlConnection conn = new SqlConnection("server=192.168.2.200;integrated security = sspi;database = northwind");

  SqlCommand cmd = new SqlCommand("insert imgtable values(@imgname,@imgData)",conn);

  SqlParameter pm = new SqlParameter("@imgname",SqlDbType.VarChar,100);

  pm.Value = filename;

  SqlParameter pm1 = new SqlParameter("@imgData",SqlDbType.Image);

  FileStream fs = new FileStream(filename,FileMode.Open);

  int len = (int)fs.Length;

  byte[] fileData = new byte[len];

  fs.Read(fileData,0,len);

  fs.Close();

  pm1.Value = fileData;

  cmd.Parameters.Add(pm);

  cmd.Parameters.Add(pm1);

  conn.Open();

  try

  {

  cmd.ExecuteNonQuery();

  }

  catch(Exception ex)

  {

  MessageBox.Show(ex.Message);

  }

  }

  private void button1_Click(object sender, System.EventArgs e)

  {

  this.openFileDialog1.ShowDialog();

  }

  /// <summary>

  /// 从数据库中读取bitmap图片并显示

  /// </summary>

  /// <param name="sender"></param>

  /// <param name="e"></param>

  private void button2_Click(object sender, System.EventArgs e)

  {

  SqlConnection conn = new SqlConnection("server=192.168.2.200;integrated security = sspi;database = northwind");

  SqlCommand cmd = new SqlCommand("select * from imgtable where imgname like '%bmp%'",conn);

  conn.Open();

  SqlDataReader dr;

  try

  {

  dr = cmd.ExecuteReader();

  dr.Read();

  System.Data.SqlTypes.SqlBinary sb = dr.GetSqlBinary(2);

  //或byte[] imageData = (byte[])dr[2];

  MemoryStream ms = new MemoryStream(sb.Value);//在内存中操作图片数据

  Bitmap bmp = new Bitmap(Bitmap.FromStream(ms));

  this.pictureBox1.Image = bmp;

  dr.Close();

  }

  catch(Exception ex)

  {

  MessageBox.Show(ex.Message);

  }

  finally

  {

  conn.Close();

  }

  }

  /// <summary>

  /// 读取文件并保存到硬盘,然后打开文件

  /// </summary>

  /// <param name="sender"></param>

  /// <param name="e"></param>

  private void button3_Click(object sender, System.EventArgs e)

  {

  SqlConnection conn = new SqlConnection("server=192.168.2.200;integrated security = sspi;database = northwind");

  SqlCommand cmd = new SqlCommand("select * from imgtable where imgname like '%doc'",conn);

  conn.Open();

  SqlDataReader dr;

  try

  {

  dr = cmd.ExecuteReader();

  dr.Read();

  System.Data.SqlTypes.SqlBinary sb = dr.GetSqlBinary(2);

  //或byte[] imageData = (byte[])dr[2];

  //FileStream fs = new FileStream(@"C: emp.bmp",FileMode.Create);

  string filename = @"C:\" + System.IO.Path.GetFileName(dr.GetString(1));

  FileStream fs = new FileStream(filename,FileMode.Create);

  fs.Write(sb.Value,0,sb.Value.Length);

  fs.Close();

  //this.pictureBox1.Image = Image.FromFile(@"C: emp.bmp");

  System.Diagnostics.Process.Start(filename);

  dr.Close();

  }

  catch(Exception ex)

  {

  MessageBox.Show(ex.Message);

  }

  finally

  {

  conn.Close();

  }

  }

  }

  }

  直接把整个文件读取到内存中的数组里对于小文件来说是没问题的,但如果是大文件,特别是大小都超过了物理内存的文件,可能会导致严重的内存问题,需要分段读取,并分段写到数据库。

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