dropdownlist将参数传递给vb.net中的webmethod

Question

我在谷歌上搜索了几天，仍然找不到解决方案。我创建了3个ASP下拉列表，在用户选择字符串后，将该字符串传递给VB.net中的SQL query的webmethod

有人能给我一些提示吗？

谢谢。

下面是代码：

 function draw2CavitiesChart() {
            var options = {
                title: '2 Line VS Cavities',
                width: 1700,
                height: 700,
                //bar: { groupWidth: "95%" },
                //curveType: 'function',
                //isStacked: true
                pointSize: 8,
                hAxis: { title: 'Date', format: 'M/d/yy' },
                vAxis: { title: 'Total Cavities' },
                //colors: ['blue'],
                legend: { position: "bottom" }
            };
           

        var vs_SelectedLine1 = ddlSelectedLine1;
        var vs_SelectedLine2 = ddlSelectedLine2;
        var vs_SelectedLine3 = ddlSelectedLine3;
        
        $.ajax({
            type: "POST",
            url: "Chart.aspx/Get2CavitiesData",         
            date: { SelectedLine1: vs_SelectedLine1, SelectedLine2: vs_SelectedLine2, SelectedLine3: vs_SelectedLine3 },
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (r) {
                var data = google.visualization.arrayToDataTable(r.d);
                var chart = new google.visualization.LineChart($("#div2CavitiesChart")[0]);
                chart.draw(data, options);
            },
            failure: function (r) {
                alert(r.d);
            },
            error: function (r) {
                alert(r.d);
            }
        });
    }

和代码背后： _公共函数Get2CavitiesDate()

    Return (Me.ddlSelectedLine1.SelectedItem.ToString)
    Return (Me.ddlSelectedLine2.SelectedItem.ToString)
    Return (Me.ddlSelectedLine3.SelectedItem.ToString)

    Dim constring As String = ConfigurationManager.ConnectionStrings("LocalDBConnectionString").ConnectionString
    Dim chartData As New List(Of Object)()
    chartData.Add(New Object() {"SelectedDate", "(SelectedLine1)", "(SelectedLine2)", "(SelectedLine3)"})
    Using con As New SqlConnection(constring)
        Using cmd As New SqlCommand()
            cmd.CommandType = CommandType.StoredProcedure
            cmd.CommandText = "ChartReportDataTable"
            cmd.Connection = con
            con.Open()
            Using sdr As SqlDataReader = cmd.ExecuteReader()
                While sdr.Read()
                    chartData.Add(New Object() {sdr("SelectedDate"), sdr("(SelectedLine1"), sdr("(SelectedLine2)"), sdr("(SelectedLine3)")})
                End While
            End Using
            con.Close()
            Return chartData
        End Using
    End Using

End Function

和ASP：

DropDownList ID="ddlSelectedLine1“runat="server”AutoPostBack="false“/>

Answer 1

您使用的是<asp:DropDownList>，因此在客户端JS中访问它的方法是使用<%= ddlSelectedLine1.ClientID %>。所以像var vs_SelectedLine1 = document.getElementById('<%= ddlSelectedLine1.ClientID %>).value这样的东西应该可以做到这一点。

此外，您将无法在代码隐藏中访问控件的值，因为任何正常的页面周期都不会执行，因此控件将具有从视图状态加载的值。

在JS客户端ajax调用中，您有一个输入错误的代码：

data: "{ 'SelectedLine1': '" + vs_SelectedLine1 + "', 'SelectedLine2': '" + vs_SelectedLine2 + "', 'SelectedLine3': '" + vs_SelectedLine3 + "' }"

您的后端代码签名将如下所示

public static <chartDataType> Get2CatvitiesDate(string SelectedLine1, string SelectedLine2, string SelectedLine3) { ... <rest of your function > }

我不知道你的后端方法的返回类型，但这应该可以让你上手。