C# Access中OLE对象的操作

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:DocumentsDatabase1.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:DocumentsDatabase1.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。