Question

我有2个国家和州的复选框列表。现在，当用户检查一个国家时，将出现的州名单仅来自该国家。但是，如果用户检查多个，我该怎么办？这是我的代码。我不知道如何在vb.net中制作for循环

cmd.CommandText = "SELECT distinct(a.AreaCode), b.AreaDescrip from tblUser a INNER JOIN tblArea b on a.AreaCode = b.AreaCode "
cmd.CommandText = cmd.CommandText & "WHERE CountryCode = N'" & Trim(Replace(cblCountry.SelectedValue, "'", "''")) & "'"""

Answer 1

正如@Dai所说，使用in query，或者使用文字值：

        'join selected items together
    Dim selectedItems = String.Join("','", cblCountry.Items.Cast(Of ListItem)().Where(Function(li) li.Selected).Select(Function(li) li.Value))

    'add joined string to command text
    cmd.CommandText = "SELECT distinct(a.AreaCode), b.AreaDescrip from tblUser a INNER JOIN tblArea b on a.AreaCode = b.AreaCode " & _
        "WHERE CountryCode IN ('" & selectedItems & "')"

或者最好使用参数化查询，在其中向命令文本添加参数名称，然后向命令对象添加参数，如下所示：

        'get selected item values
    Dim selectedItems = cblCountry.Items.Cast(Of ListItem)().Where(Function(li) li.Selected).Select(Function(li) li.Value)

    'create a named parameter for each selected item - parameter0, parameter1 and so on
    Dim parameters As String = String.Join(",", Enumerable.Range(0, selectedItems.Count()).Select(Function(x) "@parameter" + x))

    'Add parameter names to command text
    cmd.CommandText = "SELECT distinct(a.AreaCode), b.AreaDescrip from tblUser a INNER JOIN tblArea b on a.AreaCode = b.AreaCode " & _
        "WHERE CountryCode IN (" & parameters & ")"

    'add parameters to command object with values from selected items
    For p As Integer = 0 To selectedItems.Count() - 1
        cmd.Parameters.AddWithValue("@parameter" + p, selectedItems(p))
    Next

多项选择CheckBoxList

1 个答案: