在將圖像從數據庫轉換爲字節並返回到圖像時出現問題

Question

我在窗體中有一個按鈕和一個datagridview。我需要從數據庫獲取圖像並在datagrid中顯示其值，然後獲取數據網格中圖像的值以將其複製到另一個數據庫。

具體來說，我正在將database1的table1中的圖像（blob）複製到database2的表1中。

的button1_Click：

Dim img As Image 
    Dim bArr As Byte() 
Try 
      Dim Sql = "Select ID, IMG from sample" 
      connectionOnline() 
      Dim cmd = New MySqlCommand(Sql, ConOnline) 
      Dim dr = cmd.ExecuteReader(CommandBehavior.CloseConnection) 
      DataGridView1.Rows.Clear() 
      While dr.Read = True 
       img = dr(1) 
       bArr = imgToByteArray(img) 
       DataGridView1.Rows.Add(dr(0), bArr) 
      End While 
      ConOnline.Close() 
     Catch ex As Exception 
      MsgBox(ex.Message) 
     End Try 

Try 
      connectionSync() 
      Dim a, b As String 
      Dim Sql = "INSERT INTO SAMPLE (ID, IMG)values(@a,@b)" 

      For i As Integer = 0 To Me.DataGridView1.Rows.Count - 1 
       a = Me.DataGridView1.Rows(i).Cells(0).Value.ToString() 
       Dim img1 As Image = byteArrayToImage(bArr) 
       Dim cmd As New MySqlCommand(Sql, ConSync) 
       cmd.Parameters.AddWithValue("@a", a) 
       cmd.Parameters.AddWithValue("@b", img1) 
       cmd.ExecuteNonQuery() 
       cmd.Parameters.Clear() 
      Next 
      ConSync.Close() 
     Catch ex As Exception 
       MsgBox(ex.Message) 
     End Try 


Try 
      connectionSync() 
      Dim Sql = "INSERT INTO B.SAMPLE(ID, IMG) SELECT ID, IMG FROM C.SAMPLE WHERE not exists (SELECT 1 from B.SAMPLE WHERE B.SAMPLE.ID=C.SAMPLE.ID)" 
      Dim cmd = New MySqlCommand(Sql, ConSync) 
      With cmd 
       .ExecuteNonQuery() 
      End With 
      MsgBox("Success", vbInformation, "Save") 
      ConSync.Close() 
     Catch ex As Exception 
      MsgBox(ex.Message) 
     End Try 

Try 
      connectionOffline() 
      Dim Sql = "UPDATE SAMPLE SET IMG=(SELECT C.SAMPLE.NAME FROM C.SAMPLE WHERE C.SAMPLE.ID=B.SAMPLE.ID) WHERE B.SAMPLE.ID=(SELECT C.SAMPLE.ID FROM C.SAMPLE WHERE C.SAMPLE.ID=B.SAMPLE.ID)" 
      Dim cmd = New MySqlCommand(Sql, ConOffline) 
      With cmd 
       .ExecuteNonQuery() 
      End With 
      MsgBox("Success") 
      ConOffline.Close() 
     Catch ex As Exception 
      MsgBox(ex.Message) 
     End Try 

B和C是數據庫
雖然樣品是表

下面

爲i用於將圖像轉換功能

Public Function imgToByteArray(ByVal img As Image) As Byte() 
     Using mStream As New MemoryStream() 
      img.Save(mStream, img.RawFormat) 
      Return mStream.ToArray() 
     End Using 
    End Function 

    Public Function byteArrayToImage(ByVal byteArrayIn As Byte()) As Image 
     Using mStream As New MemoryStream(byteArrayIn) 
      Return Image.FromStream(mStream) 
     End Using 
    End Function 

結果（在數據庫中; IMG）只顯示：「System.Drawing.Bitmap」而不是實際圖像

Answer 1

您只存儲一個「Image.ToString」。

嘗試使用的二進制參數：

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