有时候需要大数据的存取时,如图片,需要用到ole对象的操作。
首先,在默认文件中,添加两个名空间
using System.Data.OleDb;
using System.IO;一个用于数据库操作,一个用于二进制文件操作
在Access中新建数据库Database1.mdb, 完整文件路径D:\Documents\Database1.mdb
写入OLE对象数据
打开文件,选择一个大的图像文件,然后存入数据库。
代码如下:
private void button1_Click(object sender, EventArgs e)
{ if (openFileDialog1.ShowDialog() == DialogResult.OK) { FileStream fs = new FileStream(openFileDialog1.FileName, FileMode.Open, FileAccess.Read); Byte[] buff = new Byte[fs.Length]; BinaryReader rd = new BinaryReader(fs); rd.Read(buff, 0, Convert.ToInt32(fs.Length)); OleDbCommand command = new OleDbCommand("INSERT INTO 表1 ([object], path) VALUES(@object, @path)", conn); command.Parameters.Add("@object", OleDbType.Binary, buff.Length).Value = buff; command.Parameters.Add("@path", OleDbType.Char, 255).Value = openFileDialog1.FileName; command.ExecuteNonQuery(); rd.Close(); fs.Close(); } }
读出OLE对象数据按钮
将数据库里存进的图片文件一个个读出来,另存为临时文件testfile*.png(测试用的文件都是png图片)
代码如下:
private void button2_Click(object sender, EventArgs e)
{ OleDbCommand command = new OleDbCommand("SELECT [object], path FROM 表1", conn); OleDbDataReader dr = command.ExecuteReader(); FileStream fs; BinaryWriter writer; int bufferSize = 100; byte[] outByte = new byte[bufferSize]; int i=0; while (dr.Read()) { string filename = "D:\\documents\\testfile"+ i.ToString() + ".png"; fs = new FileStream(filename, FileMode.OpenOrCreate, FileAccess.Write); writer = new BinaryWriter(fs); int startIndex = 0; long retval = dr.GetBytes(0, startIndex, outByte, 0, bufferSize); while (retval == bufferSize) { writer.Write(outByte); writer.Flush(); startIndex += bufferSize; retval = dr.GetBytes(0, startIndex, outByte, 0, bufferSize); } writer.Write(outByte, 0, (int)retval - 1); writer.Flush(); writer.Close(); fs.Close(); i++; } dr.Close(); }
此外,注意使用数据库前,先要打开数据库,用完关闭。
相关代码片段1:
OleDbConnection conn;
public Form1() { InitializeComponent(); conn = new OleDbConnection(); conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0; Data Source=d:\Documents\Database1.mdb"; conn.Open(); }
片段2:
private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{ conn.Close(); }
至此,OLE对象存取学习实践完毕,代码也已完整。