Question

我有一个数据网格视图，在更新按钮中我写了这样的代码：

Dim cid As Integer
        Dim dtid As Integer
        Dim cmpname As String
        Dim dtname As String
        Dim dtPhone As String
        Dim dtEmail As String
        Dim dtimage As Image


        For i As Integer = 0 To gv.RowCount - 2
            ' Dim rv = DirectCast(bSource.Current, DataRowView)
            Dim rv = DirectCast(gv.Rows(i).DataBoundItem, DataRowView)
            cid = rv.Row.Field(Of Integer)("Cid")

            dtid = rv.Row.Field(Of Integer)("dtId")
            cmpname = rv.Row.Field(Of String)("CompanyName")
            dtname = rv.Row.Field(Of String)("Department")
            dtPhone = rv.Row.Field(Of String)("Phone")
            dtEmail = rv.Row.Field(Of String)("Email")
            dtimage = rv.Row.Field(Of Image)("empimage")

            adapter.UpdateCommand = New SqlCommand("UPDATE CompanyMaster_tbl SET CompanyName = @CompanyName", con.connect)
            adapter.UpdateCommand = New SqlCommand("update DepartmentMaster_tbl set dtName = @dtName,dtPhone = @dtPhone,dtEmail = @dtEmail,empimage=@dtimage  where dtId=@dtid", con.connect)
            adapter.UpdateCommand.Parameters.AddWithValue("@Cid", cid)

            adapter.UpdateCommand.Parameters.AddWithValue("@CompanyName", cmpname)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtId", dtid)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtName", dtname)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtPhone", dtPhone)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtEmail", dtEmail)
            adapter.UpdateCommand.Parameters.AddWithValue("@dtimage", dtimage)
            adapter.UpdateCommand.ExecuteNonQuery()

但我在这一行得到了错误 dtimage = rv.Row.Field（Of Image）（“empimage”）：无法将'System.Byte []'类型的对象强制转换为'System.Drawing.Image'< / em>的

Answer 1

我不确定语法是100％正确所以我会继续努力，我是一名C＃程序员，但这是你需要做的：

Using ms As New MemoryStream(Row.Field(Of Byte())("empimage"))
    dtimage = New Bitmap(ms)
End Using

要将同样的Bitmap保存回数据库，您需要执行以下操作：

Using ms As New MemoryStream()
    bmp.Save(ms, ImageFormat.MemoryBmp)

    Dim bytes(ms.Length) As New Byte()
    ms.Read(bytes, 0, ms.Length)

    ' now save that Byte() to the field in the data table
End Using

注意： MemoryBmp可能无效 - 您可能需要使用更具体的内容。这是listing of them。

Answer 2

empimage包含一个字节数组，您需要从中加载图像：

dtimage = ImageFromBytes(rv.Row.Field(Of Byte())("empimage"))

...


Function ImageFromBytes(ByVal bytes As Byte()) As Image
    Using ms As New MemoryStream(bytes)
        return Image.FromStream(ms)
    End Using
End Function

无法将类型为'System.Byte []'的对象转换为在Windows应用程序中键入'System.Drawing.Image'

2 个答案: