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：
1
using System;
2using System.Drawing;
3using System.Collections;
4using System.ComponentModel;
5using System.Windows.Forms;
6using System.Data;
7using System.Data.SqlClient;
8using System.IO;
9
10namespace ADO_Demo
11
{
12
/**//// <summary>
13
/// Form1 的摘要说明。
14
/// </summary>
15 public class ADO_Demo : System.Windows.Forms.Form
16 {
17 private System.Windows.Forms.Button button1;
18 private System.Windows.Forms.Button button2;
19 private System.Windows.Forms.PictureBox pictureBox1;
20 private System.Windows.Forms.OpenFileDialog openFileDialog1;
21 private System.Windows.Forms.Button button3;
22 /**//// <summary>
23 /// 必需的设计器变量。
24 /// </summary>
25 private System.ComponentModel.Container components = null;
26
27 public ADO_Demo()
28 {
29 //
30 // Windows 窗体设计器支持所必需的
31 //
32 InitializeComponent();
33
34 //
35 // TODO: 在 InitializeComponent 调用后添加任何构造函数代码
36 //
37 }
38
39 /**//// <summary>
40 /// 清理所有正在使用的资源。
41 /// </summary>
42 protected override void Dispose( bool disposing )
43 {
44 if( disposing )
45 {
46 if (components != null)
47 {
48 components.Dispose();
49 }
50 }
51 base.Dispose( disposing );
52 }
53
54 Windows 窗体设计器生成的代码#region Windows 窗体设计器生成的代码
55 /**//// <summary>
56 /// 设计器支持所需的方法 - 不要使用代码编辑器修改
57 /// 此方法的内容。
58 /// </summary>
59 private void InitializeComponent()
60 {
61 this.button1 = new System.Windows.Forms.Button();
62 this.button2 = new System.Windows.Forms.Button();
63 this.pictureBox1 = new System.Windows.Forms.PictureBox();
64 this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();
65 this.button3 = new System.Windows.Forms.Button();
66 this.SuspendLayout();
67 //
68 // button1
69 //
70 this.button1.Location = new System.Drawing.Point(368, 48);
71 this.button1.Name = "button1";
72 this.button1.Size = new System.Drawing.Size(104, 23);
73 this.button1.TabIndex = 0;
74 this.button1.Text = "保存图片";
75 this.button1.Click += new System.EventHandler(this.button1_Click);
76 //
77 // button2
78 //
79 this.button2.Location = new System.Drawing.Point(368, 120);
80 this.button2.Name = "button2";
81 this.button2.Size = new System.Drawing.Size(104, 23);
82 this.button2.TabIndex = 1;
83 this.button2.Text = "显示图片";
84 this.button2.Click += new System.EventHandler(this.button2_Click);
85 //
86 // pictureBox1
87 //
88 this.pictureBox1.Location = new System.Drawing.Point(8, 16);
89 this.pictureBox1.Name = "pictureBox1";
90 this.pictureBox1.Size = new System.Drawing.Size(312, 288);
91 this.pictureBox1.TabIndex = 2;
92 this.pictureBox1.TabStop = false;
93 //
94 // openFileDialog1
95 //
96 this.openFileDialog1.FileOk += new System.ComponentModel.CancelEventHandler(this.openFileDialog1_FileOk);
97 //
98 // button3
99 //
100 this.button3.Location = new System.Drawing.Point(368, 200);
101 this.button3.Name = "button3";
102 this.button3.Size = new System.Drawing.Size(104, 23);
103 this.button3.TabIndex = 1;
104 this.button3.Text = "读取文件并打开";
105 this.button3.Click += new System.EventHandler(this.button3_Click);
106 //
107 // ADO_Demo
108 //
109 this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
110 this.ClientSize = new System.Drawing.Size(496, 317);
111 this.Controls.Add(this.pictureBox1);
112 this.Controls.Add(this.button2);
113 this.Controls.Add(this.button1);
114 this.Controls.Add(this.button3);
115 this.Name = "ADO_Demo";
116 this.Text = "ADO_Demo";
117 this.ResumeLayout(false);
118
119 }
120 #endregion
121
122 /**//// <summary>
123 /// 应用程序的主入口点。
124 /// </summary>
125 [STAThread]
126 static void Main()
127 {
128 Application.Run(new ADO_Demo());
129 }
130
131 /**//// <summary>
132 /// 点击打开文件对话框确定按钮，将文件保存到数据库中
133 /// </summary>
134 /// <param name="sender"></param>
135 /// <param name="e"></param>
136 private void openFileDialog1_FileOk(object sender, System.ComponentModel.CancelEventArgs e)
137 {
138 string filename = this.openFileDialog1.FileName;
139 SqlConnection conn = new SqlConnection("server=192.168.2.200;integrated security = sspi;database = northwind");
140 SqlCommand cmd = new SqlCommand("insert imgtable values(@imgname,@imgData)",conn);
141 SqlParameter pm = new SqlParameter("@imgname",SqlDbType.VarChar,100);
142 pm.Value = filename;
143 SqlParameter pm1 = new SqlParameter("@imgData",SqlDbType.Image);
144 FileStream fs = new FileStream(filename,FileMode.Open);
145 int len = (int)fs.Length;
146 byte[] fileData = new byte[len];
147 fs.Read(fileData,0,len);
148 fs.Close();
149
150 pm1.Value = fileData;
151 cmd.Parameters.Add(pm);
152 cmd.Parameters.Add(pm1);
153
154 conn.Open();
155 try
156 {
157 cmd.ExecuteNonQuery();
158 }
159 catch(Exception ex)
160 {
161 MessageBox.Show(ex.Message);
162 }
163
164
165 }
166
167 private void button1_Click(object sender, System.EventArgs e)
168 {
169 this.openFileDialog1.ShowDialog();
170 }
171
172 /**//// <summary>
173 /// 从数据库中读取bitmap图片并显示
174 /// </summary>
175 /// <param name="sender"></param>
176 /// <param name="e"></param>
177 private void button2_Click(object sender, System.EventArgs e)
178 {
179 SqlConnection conn = new SqlConnection("server=192.168.2.200;integrated security = sspi;database = northwind");
180 SqlCommand cmd = new SqlCommand("select * from imgtable where imgname like '%bmp%'",conn);
181 conn.Open();
182 SqlDataReader dr;
183 try
184 {
185 dr = cmd.ExecuteReader();
186 dr.Read();
187 System.Data.SqlTypes.SqlBinary sb = dr.GetSqlBinary(2);
188 //或byte[] imageData = (byte[])dr[2];
189 MemoryStream ms = new MemoryStream(sb.Value);//在内存中操作图片数据
190 Bitmap bmp = new Bitmap(Bitmap.FromStream(ms));
191 this.pictureBox1.Image = bmp;
192 dr.Close();
193 }
194 catch(Exception ex)
195 {
196 MessageBox.Show(ex.Message);
197 }
198 finally
199 {
200 conn.Close();
201 }
202 }
203
204 /**//// <summary>
205 /// 读取文件并保存到硬盘，然后打开文件
206 /// </summary>
207 /// <param name="sender"></param>
208 /// <param name="e"></param>
209 private void button3_Click(object sender, System.EventArgs e)
210 {
211 SqlConnection conn = new SqlConnection("server=192.168.2.200;integrated security = sspi;database = northwind");
212 SqlCommand cmd = new SqlCommand("select * from imgtable where imgname like '%doc'",conn);
213 conn.Open();
214 SqlDataReader dr;
215 try
216 {
217 dr = cmd.ExecuteReader();
218 dr.Read();
219 System.Data.SqlTypes.SqlBinary sb = dr.GetSqlBinary(2);
220 //或byte[] imageData = (byte[])dr[2];
221 //FileStream fs = new FileStream(@"C:\temp.bmp",FileMode.Create);
222 string filename = @"C:\" + System.IO.Path.GetFileName(dr.GetString(1));
223 FileStream fs = new FileStream(filename,FileMode.Create);
224 fs.Write(sb.Value,0,sb.Value.Length);
225 fs.Close();
226 //this.pictureBox1.Image = Image.FromFile(@"C:\temp.bmp");
227 System.Diagnostics.Process.Start(filename);
228 dr.Close();
229 }
230 catch(Exception ex)
231 {
232 MessageBox.Show(ex.Message);
233 }
234 finally
235 {
236 conn.Close();
237 }
238 }
239 }
240
}
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。