Question

我在一个页面中使用了三个DropDownLists。我使用if（！Page.IsPostBack）条件在pageload上将数据绑定到DDL1（DropDownList1）。在DDL1 selectedIndexChanged事件我将数据绑定到DDL2并且其工作正常。但是当我尝试对DDL3＆amp; DDL2（类似于DDL2的SelectedIndexChanged事件上的DDL2的绑定数据）总是DDL2仅在我选择随机时选择第一项，同时DDL2仍然是第一项。这里所有3个DDL都是AutoPostback-true，Vistate-Enabled

以下是我的代码：

ASPX - 代码..

<form id="form1" runat="server">
<div>    
    <br />
    <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
        <asp:ListItem Value="0">Select</asp:ListItem>
    </asp:DropDownList>
    <br />
    <br />
    <asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged">
        <asp:ListItem Value="0">Select</asp:ListItem>
    </asp:DropDownList>
    <br />
    <br />
    <asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True">
        <asp:ListItem Value="0">Select</asp:ListItem>
    </asp:DropDownList>
    <br />    
</div>
</form>

.CS代码...

public partial class getcolumns : System.Web.UI.Page
{
private SqlConnection con;
private SqlDataAdapter da;
private DataTable dt;
private DataSet ds;

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        try
        {
            string query = " SELECT name, dbid FROM sys.sysdatabases where dbid > 4 order by name ";
            con = new SqlConnection(ConfigurationManager.AppSettings["godb"].ToString());
            da = new SqlDataAdapter(query, con);
            dt = new DataTable();
            ds = new DataSet();
            da.Fill(dt);
            DropDownList1.DataSource = dt.DefaultView.ToTable(true, "name", "dbid");
            //DropDownList1.DataValueField = "dbid";
            DropDownList1.DataTextField = "name";
            DropDownList1.DataBind();
        }
        catch (Exception) { }
    }
}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    try
    {
        DropDownList2.Items.Clear();
        string query = " SELECT TABLE_CATALOG, TABLE_NAME FROM " + DropDownList1.SelectedItem + ".INFORMATION_SCHEMA.tables ";
        con = new SqlConnection(ConfigurationManager.AppSettings["godb"].ToString());
        da = new SqlDataAdapter(query, con);
        dt = new DataTable();
        ds = new DataSet();
        da.Fill(ds);
        DropDownList2.DataSource = ds; // dt.DefaultView.ToTable(true, "TABLE_NAME", "TABLE_CATALOG");
        //DropDownList2.DataValueField = "TABLE_CATALOG";
        DropDownList2.DataTextField = "TABLE_NAME";
        DropDownList2.DataBind();
        DropDownList2.Items.Insert(0, new ListItem("--Select--", "0"));
    }
    catch { }
}

protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
{
    try
    {
        DropDownList3.Items.Clear();
        string query = " SELECT TABLE_NAME, COLUMN_NAME FROM  " + DropDownList1.SelectedItem + ".INFORMATION_SCHEMA.columns where TABLE_NAME = '" + DropDownList2.SelectedItem + "' ";
        con = new SqlConnection(ConfigurationManager.AppSettings["godb"].ToString());
        da = new SqlDataAdapter(query, con);
        dt = new DataTable();
        da.Fill(dt);
        DropDownList3.DataSource = dt.DefaultView.ToTable(true, "TABLE_NAME", "COLUMN_NAME");
        //DropDownList3.DataValueField = "TABLE_NAME";
        DropDownList3.DataTextField = "COLUMN_NAME";
        DropDownList3.DataBind();
    }
    catch (Exception) { }
}
}

修改： - 当我忽略＆＃39; DataValueField ＆＃39; DDL 感谢大家的支持......

Answer 1

这可能是多个autopostback事件，因此当它首先触发时ddl1会在第二个事件中覆盖所选项目。当第二个事件发生时，它将重置为默认状态。

您可以尝试在两者上使用相同的事件方法，具体取决于调用者填充内容。

使用这两个（对象发送者，EventArgs e）：D

Answer 2

尝试使用此代码，它对我来说很好。

<强> ASPX

<form id="form1" runat="server">
    <div>
    <asp:DropDownList  ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" >
    </asp:DropDownList>
    <asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged" >
    </asp:DropDownList> 
    <asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True" >
    </asp:DropDownList>
    </div>
    </form>

<强>的.cs

    public List<string> list1 { get; set; }
    public List<string> list2 { get; set; }
    public List<string> list3 { get; set; }
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            try
            {
                list1 = new List<string> { "a", "b", "c" };
                DropDownList1.DataSource = list1;
                DropDownList1.DataBind();
            }
            catch (Exception) { }
        }
    }

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            list2 = new List<string> { "1a", "1b", "1c" };
            DropDownList2.DataSource = list2; 
            DropDownList2.DataBind();
        }
        catch { }
    }

    protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            list3 = new List<string> { "2a", "2b", "2c" };
            DropDownList3.DataSource = list3;
            DropDownList3.DataBind();
        }
        catch (Exception) { }
    }

我刚删除了下拉列表中的默认options并删除了viewstatemode并使用了数据绑定而不是列表。

asp.net级联下拉列表总是选择第一项

2 个答案: