足球游戏_中国足彩网¥体育资讯$

通过ADO.NET存取文件
来源:易贤网 阅读:751 次 日期:2014-08-20 14:00:03
温馨提示:易贤网小编为您整理了“通过ADO.NET存取文件”,方便广大网友查阅!

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。

中国足彩网信息请查看IT技术专栏

中国足彩网信息请查看网络编程
易贤网手机网站地址:通过ADO.NET存取文件
由于各方面情况的不断调整与变化,易贤网提供的所有考试信息和咨询回复仅供参考,敬请考生以权威部门公布的正式信息和咨询为准!

2025国考·省考课程试听报名

  • 报班类型
  • 姓名
  • 手机号
  • 验证码
关于我们 | 联系我们 | 人才招聘 | 网站声明 | 网站帮助 | 非正式的简要咨询 | 简要咨询须知 | 加入群交流 | 手机站点 | 投诉建议
工业和信息化部备案号:滇ICP备2023014141号-1 足球游戏_中国足彩网¥体育资讯$ 滇公网安备53010202001879号 人力资源服务许可证:(云)人服证字(2023)第0102001523号
云南网警备案专用图标
联系电话:0871-65099533/13759567129 获取招聘考试信息及咨询关注公众号:hfpxwx
咨询QQ:526150442(9:00—18:00)版权所有:易贤网
云南网警报警专用图标