将图像存储到数据库 blob；从数据库检索到 Picturebox

您好，我之前发布了此内容并获得了一些帮助，但仍然没有有效的解决方案。感谢上一个问答，我确定我的“保存到数据库”代码以及“检索到图片”代码有问题。即使我手动将图片保存在数据库中，它仍然无法检索。这是我根据网络上的 3 或 4 个示例拼凑而成的代码。理想情况下，如果有人有一些已知的良好代码并且可以指导我使用它，那将是最好的。

    Dim filename As String = txtName.Text + ".jpg"
    Dim FileSize As UInt32
    Dim ImageStream As System.IO.MemoryStream

    ImageStream = New System.IO.MemoryStream
    PbPicture.Image.Save(ImageStream, System.Drawing.Imaging.ImageFormat.Jpeg)
    ReDim rawdata(CInt(ImageStream.Length - 1))
    ImageStream.Position = 0
    ImageStream.Read(rawdata, 0, CInt(ImageStream.Length))
    FileSize = ImageStream.Length

    Dim query As String = ("insert into actors (actor_pic, filename, filesize) VALUES    (?File, ?FileName, ?FileSize)")
    cmd = New MySqlCommand(query, conn)
    cmd.Parameters.AddWithValue("?FileName", filename)
    cmd.Parameters.AddWithValue("?FileSize", FileSize)
    cmd.Parameters.AddWithValue("?File", rawData)

    cmd.ExecuteNonQuery()

    MessageBox.Show("File Inserted into database successfully!", _
    "Success!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)

![在此输入图像描述][1]

'*****使用以下代码检索图片框：

  Private Sub GetPicture()
    'This retrieves the pictures from a mysql DB and buffers the rawdata into a memorystream 

    Dim FileSize As UInt32
    Dim rawData() As Byte

    Dim conn As New MySqlConnection(connStr)


    conn.Open()
    conn.ChangeDatabase("psdb")


    Dim cmd As New MySqlCommand("SELECT actor_pic, filesize, filename FROM actors WHERE actor_name = ?autoid", conn)
    Cmd.Parameters.AddWithValue("?autoid", Actor1Box.Text)

    Reader = cmd.ExecuteReader
    Reader.Read()

    'data is in memory 

    FileSize = Reader.GetUInt32(Reader.GetOrdinal("filesize"))
    rawData = New Byte(FileSize) {}

    'get the bytes and filesize 

    Reader.GetBytes(Reader.GetOrdinal("actor_pic"), 0, rawData, 0, FileSize)

    Dim ad As New System.IO.MemoryStream(100000)
    ' Dim bm As New Bitmap

    ad.Write(rawData, 0, FileSize)

    Dim im As Image = Image.FromStream(ad) * "error occurs here" (see below)
    Actor1Pic.Image = im


    Reader.Close()


    conn.Close()
    conn.Dispose()

    ad.Dispose()

好吧，自从没有得到帮助后，我就解决了这个问题，并最终让它发挥作用。这是我的工作代码。

从 Picturebox 中保存到 MySQL (pbPicture)

    Dim filename As String = txtName.Text + ".jpg"
    Dim FileSize As UInt32

    conn.Close()

    Dim mstream As New System.IO.MemoryStream()
    PbPicture.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)
    Dim arrImage() As Byte = mstream.GetBuffer()

    FileSize = mstream.Length
    Dim sqlcmd As New MySqlCommand
    Dim sql As String
    mstream.Close()

    sql = "insert into [your table]  (picture, filename, filesize) 
                               VALUES(@File, @FileName, @FileSize)"

    Try
        conn.Open()
        With sqlcmd
            .CommandText = sql
            .Connection = conn
            .Parameters.AddWithValue("@FileName", filename)
            .Parameters.AddWithValue("@FileSize", FileSize)
            .Parameters.AddWithValue("@File", arrImage)

            .ExecuteNonQuery()
        End With
    Catch ex As Exception
        MsgBox(ex.Message)
    Finally
        conn.Close()
    End Try

从 MySQL 数据库加载回到 Picturebox

   Dim adapter As New MySqlDataAdapter
    adapter.SelectCommand = Cmd

    data = New DataTable

    adapter = New MySqlDataAdapter("select picture from [yourtable]", conn)

笔记！！只能在图片框中放入一张图片，因此显然此查询只能为您返回一条记录

    commandbuild = New MySqlCommandBuilder(adapter)
    adapter.Fill(data)

    Dim lb() As Byte = data.Rows(0).Item("picture")
    Dim lstr As New System.IO.MemoryStream(lb)
    PbPicture.Image = Image.FromStream(lstr)
    PbPicture.SizeMode = PictureBoxSizeMode.StretchImage
    lstr.Close()