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DropdownList 在加载时重置为索引 0

发布于 2024-07-15 19:22:07 字数 311 浏览 6 评论 0原文

每次在 Firefox 中“重新加载”页面（按 F5）时，如何将我的 asp:DropDownList 元素（具有 runat="server"）重置为索引 0 ）？

如果您建议使用 JavaScript，请注意，

我没有使用表单，
我不知道如何使用 JavaScript 访问具有 runat="server" 的元素，

如果可以使用 JavaScript 上的脚本来完成此操作.aspx 页面请解释一下。

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我三岁 2024-07-22 19:22:07

将代码放入 Page_Load 事件中以执行此操作

protected void Page_Load(object sender, EventArgs e)
{    
    myDropDownList.SelectedIndex =0;
}

编辑：< /strong>

针对您的评论，如果您将上述逻辑放在 if 语句中以检查是否 Page.IsPostback = false，则刷新时所选索引将不会设置回 0 （执行客户端回发）。作为演示这一点的示例，这是一个下拉列表设置为选择后自动回发的页面

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>My Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="ddl" runat="server" AutoPostBack="true" >
        </asp:DropDownList>
    </div>
    </form>
</body>
</html>

这是后面的代码

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Init(object sender, EventArgs e)
    {
        //Apologies for Dairy Produce inspired list
        ddl.Items.Add(new ListItem("Cheese"));
        ddl.Items.Add(new ListItem("Yoghurt"));
        ddl.Items.Add(new ListItem("Milk"));
        ddl.Items.Add(new ListItem("Butter"));
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        //Run the Page with this in first, then comment out
        //the if statement to leave only ddl.SelectedIndex = 0;

        if (!Page.IsPostBack)
        {
            ddl.SelectedIndex = 0;
        }
    }
}

正如将要演示的，当页面最初运行时，刷新后，所选索引将保留在下拉列表中; 然而，当 if 语句被注释掉时，刷新后，所选索引将设置为 0（在本例中为 Cheese）。

put code in the Page_Load event to do this

protected void Page_Load(object sender, EventArgs e)
{    
    myDropDownList.SelectedIndex =0;
}

EDIT:

In response to your comments, If you have put the above logic inside of an if statement to check whether Page.IsPostback = false, then the selected index will not be set back to 0 upon refresh (which performs a client postback). As an example to demonstrate this, here is a page with a dropdown list set to autopostback upon selection

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>My Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="ddl" runat="server" AutoPostBack="true" >
        </asp:DropDownList>
    </div>
    </form>
</body>
</html>

Here is the code behind

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Init(object sender, EventArgs e)
    {
        //Apologies for Dairy Produce inspired list
        ddl.Items.Add(new ListItem("Cheese"));
        ddl.Items.Add(new ListItem("Yoghurt"));
        ddl.Items.Add(new ListItem("Milk"));
        ddl.Items.Add(new ListItem("Butter"));
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        //Run the Page with this in first, then comment out
        //the if statement to leave only ddl.SelectedIndex = 0;

        if (!Page.IsPostBack)
        {
            ddl.SelectedIndex = 0;
        }
    }
}

As will be demonstrated, when the page is originally ran, upon refresh, the selected index will be retained within the dropdown list; When the if statement is commented out however, upon refresh, the selected index is set to 0 (which in this case is Cheese).

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可可 2024-07-22 19:22:07

只需将此代码添加到您的 Page_Load 事件中：

if (myDropDown.Items.Count > 0)
{
    myDropDown.Items[myDropDown.SelectedIndex].Selected = false;
    myDropDown.Items[0].Selected = true;
}

Just add this code to your Page_Load event :

if (myDropDown.Items.Count > 0)
{
    myDropDown.Items[myDropDown.SelectedIndex].Selected = false;
    myDropDown.Items[0].Selected = true;
}

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流星番茄 2024-07-22 19:22:07

在您的脚本中，在 HTML 代码下：

B01 = document.getElementById('<%=me.yourID.clientid %>');
B01.selectedIndex = 0;

Happy Coding ^^

In your script under code HTML:

B01 = document.getElementById('<%=me.yourID.clientid %>');
B01.selectedIndex = 0;

Happy Coding ^^

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心是晴朗的。 2024-07-22 19:22:07

阻止 Firefox 保留视图状态并重新填充表单：

    protected void Page_Load(object sender, EventArgs e)
    {
        if (Request.Browser.Browser == "Firefox")
            Form.Attributes.Add("autocomplete", "off");
    }

stop Firefox from retaining the viewstate and repopulating the form:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (Request.Browser.Browser == "Firefox")
            Form.Attributes.Add("autocomplete", "off");
    }

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~没有更多了~