如何獲取/加載blob圖像使用

Question

我試圖加載一個圖像，longblob字段，我有我的表中的1行（ID，設計，名稱）數據。但是當我點擊按鈕來顯示圖像，但它沒有顯示它。

我有一個GetImage.aspx打電話給我的方法

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
    Try 
     Using conn As New MySqlConnection(ConfigurationManager.ConnectionStrings("MySQLConnection").ToString()) 
      cmd = New MySqlCommand("SELECT design FROM mytable") 
      Dim imageData As Byte() = DirectCast(cmd.ExecuteScalar(), Byte()) 
      conn.Open() 
      Context.Response.Clear() 
      Context.Response.ContentType = "image/jpeg" 
      Context.Response.BinaryWrite(imageData) 
      Context.Response.End() 

     End Using 

    Catch ex As Exception 
    End Try 
End Sub 

這是我的控制按鈕，從我的默認頁面顯示的圖像

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click 
    Image1.ImageUrl = "GetImage.aspx?" 
End Sub 

請幫助我不明白爲什麼我的形象未顯示

Answer 1

這些線路故障：

Dim imageData As Byte() = DirectCast(cmd.ExecuteScalar(), Byte()) 
conn.Open() 

您需要在執行命令之前打開連接：

conn.Open() 
Dim imageData As Byte() = DirectCast(cmd.ExecuteScalar(), Byte()) 

你也需要用命令連接關聯：

cmd = New MySqlCommand("SELECT design FROM mytable", conn)