如何将可用记录数附加到下拉列表选项？

Question

我希望我的帖子的标题有意义。

我们正在构建一个汽车经销商网络应用程序，让潜在的汽车购买者能够确定哪种类型的汽车适合他们的预算和需求。

因此，我们有汽车品牌、汽车型号、汽车状况、里程、价格范围等的下拉列表。

下面的代码显示了汽车品牌的下拉列表。

当用户选择他/她喜欢的汽车品牌时，与该品牌关联的车型会自动加载到第二个下拉列表中。

    <form id="form1" runat="server">
    <div>
        <span style ="font-family:Arial">Select Make : </span> 
        <asp:DropDownList ID="ddlMake" runat="server" AutoPostBack = "true" OnSelectedIndexChanged="ddlMake_SelectedIndexChanged">
        <asp:ListItem Text = "------" Value = ""></asp:ListItem>
        </asp:DropDownList>
        <br /><br />
        <span style ="font-family:Arial">Select Model : </span> 
        <asp:DropDownList ID="ddlModel" runat="server" Enabled = "false" AutoPostBack = "true" OnSelectedIndexChanged="ddlModel_SelectedIndexChanged">
        <asp:ListItem Text = "------" Value = ""></asp:ListItem>
        </asp:DropDownList>
        <br /><br />
        <asp:button id="btnSave" runat="server" Text="Submit New Request"></asp:button><br /><br />
        <asp:Label ID="lblResults" runat="server" Text="" Font-Names = "Arial"></asp:Label>        
    </div>
    </form>



     Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
            If Not IsPostBack Then
                ddlMake.AppendDataBoundItems = True
                Dim strConnString As [String] = ConfigurationManager _
                 .ConnectionStrings("amsconstr").ConnectionString
                Dim strQuery As [String] = "select vehicleId, Make from MakeModel"
                Dim con As New SqlConnection(strConnString)
                Dim cmd As New SqlCommand()
                cmd.CommandType = CommandType.Text
                cmd.CommandText = strQuery
                cmd.Connection = con
                Try
                    con.Open()
                    ddlMake.DataSource = cmd.ExecuteReader()
                    ddlMake.DataTextField = "Make"
                    ddlMake.DataValueField = "vehicleId"
                    ddlMake.DataBind()
                Catch ex As Exception
                    Throw ex
                Finally
                    con.Close()
                    con.Dispose()
                End Try
            End If
        End Sub
   Protected Sub ddlMake_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
            ddlModel.Items.Clear()
            ddlModel.Items.Add(New ListItem("--Select Model--", ""))

            ddlModel.AppendDataBoundItems = True
            Dim strConnString As [String] = ConfigurationManager _
                       .ConnectionStrings("amsconstr").ConnectionString
            Dim strQuery As [String] = "select vehicleId Employee from MakeModel " _
                                        & "where vehicleId=@vehicleId"
            Dim con As New SqlConnection(strConnString)
            Dim cmd As New SqlCommand()
            cmd.Parameters.AddWithValue("@vehicleId", _
                                 ddlMake.SelectedItem.Value)
            cmd.CommandType = CommandType.Text
            cmd.CommandText = strQuery
            cmd.Connection = con
            Try
                con.Open()
                ddlModel.DataSource = cmd.ExecuteReader()
                ddlModel.DataTextField = "Model"
                ddlModel.DataValueField = "VehicleId"
                ddlModel.DataBind()
                If ddlModel.Items.Count > 1 Then
                    ddlModel.Enabled = True
                Else
                    ddlModel.Enabled = False
                End If
            Catch ex As Exception
                Throw ex
            Finally
                con.Close()
                con.Dispose()
            End Try
        End Sub
  Protected Sub ddlModel_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)

            Dim strConnString As [String] = ConfigurationManager.ConnectionStrings("conString").ConnectionString
            Dim strQuery As [String] = "select VehicleId, Model from MakeModel where VehicleId=@vehicleId"
            Dim con As New SqlConnection(strConnString)
            Dim cmd As New SqlCommand()
            cmd.Parameters.AddWithValue("@vehicleId", ddlModel.SelectedItem.Value)
            cmd.CommandType = CommandType.Text
            cmd.CommandText = strQuery
            cmd.Connection = con
            Try
                con.Open()
            Catch ex As Exception
                Throw ex
            Finally

                con.Close()
                con.Dispose()
            End Try
    End Sub

这很好用。

我们想附加每种汽车品牌的可用记录数。

例如，在汽车品牌下拉列表中，我们有如下内容：

马自达 奔驰 丰田， 等等

我们希望用户知道特定品牌如何可用，例如：

Mazda (10)
Mercedez Benz (2)
Toyota (7)

如何为特定品牌的汽车添加可用汽车数量？

Answer 1

您需要使用 CONVERT() 函数。

select VehicleId, (Model + '(' + CONVERT(NVARCHAR, (select count(*) from MakeModel B where a.ID=b.ID)) + ')') as Make from MakeModel A

Answer 2

更改您的 SQL 语句，使其返回您需要的所有内容。而不仅仅是：

select VehicleId, Model from MakeModel.....

使用类似的东西：

select VehicleId, (Model + '(' + (select count(*) from MakeModel B where a.ID=b.ID) + ')') as Make from MakeModel A...

..这不是很好，但会工作。使用 SQL Server CTE 使代码更好。或者甚至更好地将最终代码放入存储过程并调用此过程。

还有一个注意事项 - 尽量减少重复代码。希望对您有所帮助。