如何使用 vb.net 和 adodb 连接在 mysql 数据库中插入图像

Question

我想在 vb.net 2008 中使用 adodb 连接将图像插入 mysql 数据库。

我正在使用选择查询将数据插入数据库，这是我添加或保存数据的代码...

    rs.Open("select * from registration where Debt_ID = '" & txtDebt_ID.Text & "' ", cnn, ADODB.CursorTypeEnum.adOpenStatic, ADODB.LockTypeEnum.adLockPessimistic)
    If rs.RecordCount = 1 Then
        MsgBox("ID already exist!", MsgBoxStyle.Exclamation, vbOK)
        rs.Close()
        cnn.Close() 

        Exit Sub
    Else

        rs.AddNew()
        rs.Fields("Debt_ID").Value = txtDebt_ID.Text
        rs.Fields("LastName").Value = txt_Lastname.Text
        rs.Fields("firstName").Value = txt_Firstname.Text
        rs.Fields("MiddleName").Value = txt_Middlename.Text
        rs.Fields("age").Value = txt_Age.Text
        rs.Fields("birthdate").Value = txt_Birthdate.Text
        rs.Fields("civil_status").Value = txtCivil_status.Text
        rs.Fields("address").Value = txt_Address.Text
        rs.Fields("occupation").Value = txt_Address.Text
        rs.Fields("contact_no").Value = txt_Contact.Text
        'rs.Fields("picture").Value = PictureBox1.Image
        rs.Save()
        rs.Close()
    End If

我想将数据库上的图像添加到字段图片中，并且我使用 blob 作为我的数据类型，我还想从数据库中检索图像并将其显示在图片框中...有人可以吗关于我的问题的帮助。

提前谢谢...

Answer 1

无论您使用什么数据访问技术或数据库，您都需要先将 Image 转换为 Byte 然后保存。在检索时，您将Byte 数组转换回Image。

保存：

Dim connection As New SqlConnection("connection string here")
Dim command As New SqlCommand("UPDATE MyTable SET Picture = @Picture WHERE ID = 1", connection)

'Create an Image object.'
Using picture As Image = Image.FromFile("file path here")
    'Create an empty stream in memory.'
    Using stream As New IO.MemoryStream
        'Fill the stream with the binary data from the Image.'
        picture.Save(stream, Imaging.ImageFormat.Jpeg)

        'Get an array of Bytes from the stream and assign to the parameter.'
        command.Parameters.Add("@Picture", SqlDbType.VarBinary).Value = stream.GetBuffer()
    End Using
End Using

connection.Open()
command.ExecuteNonQuery()
connection.Close()

检索：

Dim connection As New SqlConnection("connection string here")
Dim command As New SqlCommand("SELECT Picture FROM MyTable WHERE ID = 1", connection)

connection.Open()

Dim pictureData As Byte() = DirectCast(command.ExecuteScalar(), Byte())

connection.Close()

Dim picture As Image = Nothing

'Create a stream in memory containing the bytes that comprise the image.'
Using stream As New IO.MemoryStream(pictureData)
    'Read the stream and create an Image object from the data.'
    picture = Image.FromStream(stream)
End Using

该示例适用于 ADO.NET 和 SQL Server，但无论如何使用 MemoryStream 进行转换的原理都是相同的。

Answer 2

创建一个带有BLOB字段的表，如下所示

CREATE TABLE picture (
ID   INTEGER AUTO_INCREMENT,
IMAGE   BLOB, 
PRIMARY KEY (ID)
);

使用以下查询字符串插入此表：

Dim mstream As New System.IO.MemoryStream()
pic_box_save.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)
Dim arrImage() As Byte = mstream.GetBuffer()
mstream.Close()
Try
 sql = "INSERT INTO image_in_db(id, image_data) VALUES(@image_id, @image_data)"
 sql_command = New MySqlClient.MySqlCommand(sql, sql_connection)
 sql_command.Parameters.AddWithValue("@image_id", Nothing)
 sql_command.Parameters.AddWithValue("@image_data", arrImage)
 sql_command.ExecuteNonQuery()
Catch ex As Exception
 MsgBox(ex.Message)
 Exit Sub
End Try
MsgBox("Image has been saved.")