如何通过 ASP.NET、c# 中的另一个下拉列表过滤下拉列表值 [英] How to filter dropdown list values by another dropdown list in ASP.NET, c#

问题描述

我有一个关于过滤器的简单问题.我有 4 个下拉列表，它们从 MySQL 数据库表中过滤我的 Web 应用程序中的数据.第一个下拉列表已被选中，仅显示一个 project_id，但其他下拉列表显示了数据库中所有可能的值——这是我目前所做的.

I have a simple question about filters. I have 4 dropdown lists which filter the data in my web application from MySQL database table. The first dropdown list is already selected showing only one project_id but the others drop down lists displays all the possible values from the database - this is what I made so far.

但我只想显示所选特定项目的数据值.

But I want to display only the data values for that particular project selected.

它是 ASP.NET 4.0，背后是 C# 和 MySQL 数据库.任何帮助将不胜感激.谢谢

It's ASP.NET 4.0, C# behind and MySQL database used. Any help will be appreciated. Thanks

推荐答案

查看以下链接以填充级联下拉列表.

check out following links for populating cascading drop down list.

http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/CascadingDropDown/CascadingDropDown.aspx

http://www.codeproject.com/KB/aspnet/CascadingDropDown.aspx

http://www.aspsnippets.com/文章/Creating-Cascading-DropDownLists-in-ASP.Net.aspx

代码:

<table>
    <tr>
        <td>First</td>
        <td><asp:DropDownList ID="DDLFirst" runat="server"  AutoPostBack="true"
                onselectedindexchanged="DDLFirst_SelectedIndexChanged"></asp:DropDownList></td>
    </tr>
    <tr>
        <td>Secord</td>
        <td><asp:DropDownList ID="DDLSecond" runat="server" AutoPostBack="true"
                onselectedindexchanged="DDLSecond_SelectedIndexChanged">
            <asp:ListItem Text="Select" Value="Select"></asp:ListItem>    
            </asp:DropDownList></td>
    </tr>
    <tr>
        <td>Thrid</td>
        <td><asp:DropDownList ID="DDLThird" runat="server"><asp:ListItem Text="Select" Value="Select"></asp:ListItem>    </asp:DropDownList></td>
    </tr>
</table>

//后面的代码protected void Page_Load(object sender, EventArgs e){如果 (!IsPostBack){//绑定第一个下拉列表的代码

// Code behind protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { // your code to bind the first drop downlist

        }
    }

    protected void DDLFirst_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (DDLFirst.SelectedIndex > 0)
        {
            string FirstDDLValue = DDLFirst.SelectedItem.Value;
            // below your code to get the second drop down list value filtered on first selection


        }

    }

    protected void DDLSecond_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (DDLSecond.SelectedIndex > 0)
        {
            string SecondDDLValue = DDLSecond.SelectedItem.Value;
            // below your code to get the third drop down list value filtered on Second selection


        }
    }

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