vb.net 教程 8-3 数据库操作11

数据新增、删除和修改操作差不多。

无非就是新建sql语句，执行command.ExecuteNonQuery

本节例子使用的是NorthWind中的类别表。

有了前面查询和修改的知识，相信大家可以看懂下面的代码：

    Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click        Dim odc As New OleDbConnection()        odc.ConnectionString = "Provider = Microsoft.ACE.OLEDB.12.0;data source=Northwind.mdb;"        Dim odcommand As New OleDbCommand()        odcommand.CommandText = "insert into 类别(类别名称,说明,图片) values(@typename,@typeinfo,@imgType)"        odcommand.Connection = odc        odc.Open()        odcommand.Parameters.Add("@typename", OleDbType.VarChar)        odcommand.Parameters("@typename").Value = txtName.Text        odcommand.Parameters.Add("@typeinfo", OleDbType.VarChar)        odcommand.Parameters("@typeinfo").Value = txtInfo.Text        Dim bmp As New Bitmap(200, 100)        Dim g As Graphics = Graphics.FromImage(bmp)        g.DrawImage(picType.Image, New Rectangle(0, 0, picType.Width, picType.Height), New Rectangle(0, 0, picType.Image.Width, picType.Image.Height), GraphicsUnit.Pixel)        g.Dispose()        Dim ms As New IO.MemoryStream()        bmp.Save(ms, Imaging.ImageFormat.Bmp)        PictureBox1.Image = bmp        Dim buff() As Byte        ReDim buff(ms.Length)        buff = ms.ToArray        ms.Close()        odcommand.Parameters.Add("@imgType", OleDbType.LongVarBinary)        odcommand.Parameters("@imgType").Value = buff        odcommand.ExecuteNonQuery()        odc.Close()    End Sub

以上代码将二进制数据写入类别表中的图片列中。但是由于northwind数据库中的图片保存的和一般的图片略有区别，需要增加部分数据

要加入的数据：

    Private Function getoledata() As Byte()        Dim oledatastring As String = "151C2F00020000000D000E0014002100FFFFFFFF4269746D617020496D616765005061696E742E5069637475726500010500000200000007000000504272757368000000000000000000A0290000"        Dim datalength As Integer = oledatastring.Length        Dim buff() As Byte        ReDim buff(datalength \ 2 - 1)        For i As Integer = 0 To datalength - 1 Step 2            buff(i \ 2) = Convert.ToInt32(oledatastring.Substring(i, 2), 16)        Next        Return buff    End Function

修改后的代码：

  Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click        Dim odc As New OleDbConnection()        'odc.ConnectionString = "Provider = Microsoft.ACE.OLEDB.12.0;data source=D:\save\博客教程\08 数据库\Northwind1.mdb;jet oledb:database password=northwind;"        odc.ConnectionString = "Provider = Microsoft.ACE.OLEDB.12.0;data source=Northwind.mdb;"        Dim odcommand As New OleDbCommand()        odcommand.CommandText = "insert into 类别(类别名称,说明,图片) values(@typename,@typeinfo,@imgType)"        odcommand.Connection = odc        odc.Open()        odcommand.Parameters.Add("@typename", OleDbType.VarChar)        odcommand.Parameters("@typename").Value = txtName.Text        odcommand.Parameters.Add("@typeinfo", OleDbType.VarChar)        odcommand.Parameters("@typeinfo").Value = txtInfo.Text        Dim bmp As New Bitmap(172, 120)        Dim g As Graphics = Graphics.FromImage(bmp)        g.DrawImage(picType.Image, New Rectangle(0, 0, 172, 120), New Rectangle(0, 0, picType.Image.Width, picType.Image.Height), GraphicsUnit.Pixel)        g.Dispose()        Dim ms As New IO.MemoryStream()        bmp.Save(ms, Imaging.ImageFormat.Bmp)        Dim olebodybuff() As Byte        ReDim olebodybuff(ms.Length)        ms.Position = 0        'ms.Write(olebodybuff, 0, ms.Length)        olebodybuff = ms.ToArray        ms.Close()        Dim oleheadbuff() As Byte        oleheadbuff = getoledata()        Dim olebuff() As Byte        ReDim olebuff(olebodybuff.Length + oleheadbuff.Length - 1)        oleheadbuff.CopyTo(olebuff, 0)        olebodybuff.CopyTo(olebuff, oleheadbuff.Length)        odcommand.Parameters.Add("@imgType", OleDbType.LongVarBinary)        odcommand.Parameters("@imgType").Value = olebuff        odcommand.ExecuteNonQuery()        odc.Close()    End Sub

非常遗憾的是，在access中可以直接在画图中打开原有的图片，但是似乎新增的图片不能打开。

但是可以在 vb.net 教程 8-3 数据库操作9-1 的例子中打开

由于.net平台下C#和vb.NET很相似，本文也可以为C#爱好者提供参考。

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