無法在Windows應用程序中將類型為“ System.Byte []”的對象轉換為類型為“ System.Drawing.Image”的對象

Question

我有一個數據網格視圖，在更新按鈕中，我編寫了如下代碼：

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()

但是我在這一行中出現錯誤dtimage = rv.Row.Field（Of Image）（“ empimage”） ： 無法將類型為'System.Byte []'的對象轉換為類型為'System.Drawing.Image'

Answer 1

我不確定語法是否100％正確，所以我將繼續處理，我是一名C＃程序員，但這是您需要做的：

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

---

要將同Bitmap保存回數據庫，您需要執行以下操作：

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可能無法工作-您可能需要使用更具體的內容。 這是他們的清單 。

Answer 2

empimage包含一個字節數組，您需要從中加載圖像：

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