如何通过单击按钮在不回发的情况下获取下拉选择的索引值

Question

下面的代码； 代码不返回值空字符串

private void DisplayDplace()
    {
        BusinessLogicLayer.Businesslogiclayer objll = new BusinessLogicLayer.Businesslogiclayer();
    DataSet ds = objll.Binddname();
    drpfromplace.DataSource = ds;
    drpfromplace.DataTextField = "dname";
    drpfromplace.DataValueField = "did";
    drpfromplace.DataBind();
    drptoplace.DataSource = ds;
    drptoplace.DataTextField = "dname";
    drptoplace.DataValueField = "did";
    drptoplace.DataBind();
}

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        DisplayDplace();
    }
}

protected void Calendar1_SelectionChanged1(object sender, EventArgs e)
{
    TextBox1.Text = Calendar1.SelectedDate.ToShortDateString();
}

protected void Button1_Click(object sender, EventArgs e)
{
    Session["doj"] = TextBox1.Text;
    Session["noofseats"] = DropDownList6.SelectedItem.ToString();
    Session["fd"]= drpfromplace.SelectedItem.Value.ToString();
    Session["td"] = drptoplace.SelectedItem.Value.ToString();
}      

}

Answer 1

如果您想在不回发的情况下获得下拉列表的值，则必须使用 javascript/jquery 等客户端脚本。如果您想在后面的代码中获取值，则需要创建一个 ajax 调用。

在后面的代码中创建一个 webmethod：

[WebMethod]
        public static string MyWebMethod(string name )
        {
            /your logic goes here
            return ("Yeey");
        }

现在在 aspx.cs 上创建一个 Ajax 调用：

$('#mybutton').on('click',function(){

 $.ajax({
            type: "POST",
            url: "Default.aspx/MyWebMethod",
            data: JSON.stringify({ name: $('#drpname').val() }),
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            async: true,
            success: function (data, status) {
                alert("victory");
            },               
            failure: function (data) {
                alert(data.d);
            },
            error: function (data) {
                alert(data.d);
            }
        });

});

Answer 2

您可以将ScriptManager 添加到页面并将代码包装在UpdatePanel 中。

   <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>

    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>

            <asp:DropDownList ID="DropDownList1" runat="server">
                <asp:ListItem Text="A" Value="a"></asp:ListItem>
                <asp:ListItem Text="B" Value="b"></asp:ListItem>
            </asp:DropDownList>
            <br />
            <asp:Button ID="Button1" runat="server" Text="getValue" OnClick="Button1_Click" />
            <br />
            <asp:Label ID="Label1" runat="server" Text=""></asp:Label>

        </ContentTemplate>
    </asp:UpdatePanel>

后面的代码和往常一样工作。

    protected void Button1_Click(object sender, EventArgs e)
    {
        Label1.Text = DropDownList1.SelectedValue;
    }