Question

如何正确分配文本框，下拉列表和＆amp;通过SQL语句成功检索记录时，标签到适当的字段？我有4张桌子和1张桌子。因此，分配的数据与控件不匹配。（VS2008）

我有以下内容：

myCmd.CommandText = "SELECT pc.product_category_id, pc.product_category_name, pi.product_image_id, pi.product_image_filename, qr.qrcode_id, qr.qrcode_image_filename, p.product_author FROM Product AS p INNER JOIN ProductCategory AS pc ON p.product_category_id = pc.product_category_id INNER JOIN ProductImage AS pi ON p.product_image_id = pi.product_image_id INNER JOIN  QRCode AS qr ON p.qrcode_id = qr.qrcode_id WHERE p.product_id = '" & DropDownList2.Text & "'"

myCmd.Parameters.Add(New SqlParameter("@product_id", (DropDownList2.Text)))
myConn.Open()
'run the query and obtain a reader to get the results 
dtrReader = myCmd.ExecuteReader()

'check if there are results
If (dtrReader.Read()) Then
   'populate the values of the controls
   lblProductID2.Text = dtrReader(0)
   txtProductName2.Text = dtrReader(4)
   txtProductTitle2.Text = dtrReader(7)
   txtProductDescription2.Text = dtrReader(8)
   txtProductAuthor2.Text = dtrReader(12)

Answer 1

至少有两种方法可以解决这个问题：

1）从datareader检索时显式使用列的名称：

lblProductID2.Text = dtrReader("product_category_id")
' etc

2）遍历阅读器中的每个字段并使用case语句分配值

For nI As Integer = 0 To dtrReader.FieldCount - 1
   Select Case dtrReader.GetName(nI).ToLower()
      Case "product_category_id"
         If Not dtrReader.IsDBNull(nI) Then
             lblProductID2.Text = dtrReader.GetString(nI)
         Else
             lblProductID2.Text = String.Empty
         End If

      ' etc

   End Select
Next

数字2可能稍好一些，因为它可以更容易地在返回的数据中测试DBNull值：

正确地将数据分配给控件，SQL Server，VS2008

1 个答案: