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通过ADO.NET存取文件

 2006-07-13 17:48:58 来源:WEB开发网   
核心提示: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,通过ADO.NET存取文件,这要用到Image数据类型,可以保存多达2G的数据,可能会导致严重的内存问题,需要分段读取,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

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:\temp.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:\temp.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。

http://maxianghui.cnblogs.com/archive/2006/07/12/448943.html

Tags:通过 ADO NET

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