如何ASP.net的dropdownlist指数从前端设置为0 [英] How to set ASP.net dropdownlist index to 0 from the front-end

问题描述

我在ASP.net页面下面code：

I have the following code in ASP.net page:

<asp:DropDownList ClientIDMode="Static" ID="ddl1" CssClass="chosen-select le" runat="server" AppendDataBoundItems="true"></asp:DropDownList>
<asp:DropDownList ClientIDMode="Static" ID="ddl2" CssClass="chosen-select le" runat="server" AppendDataBoundItems="true"></asp:DropDownList>
<asp:DropDownList ClientIDMode="Static" ID="ddl3" CssClass="chosen-select le" runat="server" AppendDataBoundItems="true"></asp:DropDownList>

<input type="button" id="ClearForm" value="Clear" class="btn1" />

JQuery的来设置索引为0的所有三个的dropdownlist：

JQuery to set the index to 0 for all three dropdownlist:

$(function () {
    $("body").on("click", "#ClearForm", function (e) {
        e.preventDefault();
        $("select#ddl1, select#ddl2, select#ddl3").prop('selectedIndex', 0); //does not set the selected index to 0
        alert($("select#ddl1").text()); //displays all the options from #ddl1
    });
});

我

如何修改，以便将DropDownList索引被设置为0。

How can I modify so the dropdownlist index is set to 0.

HTML渲染第一个DropDownList的：

HTML render of the first dropdownlist:

<select name="ctl00$BodyPlaceHolder$ddl1" id="ddl1" class="le">
    <option value="Select a State">Select a State</option>
    <option value="Alabama">AL</option>
    <option value="Alaska">AK</option>
    <option value="Arizona">AZ</option>
</select>

我尝试以下jQuery和它返回空：

alert($("select#ddl1").val());

也试过以下，并没有工作：

Also tried the following and it didn't work:

$('select').each(function () {
    $(this).find('option:first').prop('selected', 'selected');
});

添加下面的JavaScript：

Added the following JavaScript:

function setSelectedIndex(dropdownlist, selVal) {
    var ddl1 = document.getElementById(dropdownlist);
    alert(ddl1.selectedIndex);
    if (ddl1.length >= selVal) { //if the selected value is greater then 0, the alert is shown but the value is not set back to 0.
        ddl1.selectedIndex = selVal;
        alert("greater or equal");
    }
    else {
        alert("not greater or equal");
    }
}

这似乎是，如果我删除选定的jQuery的正常工作： http://jsfiddle.net/bpbvhsay/

推荐答案

我使用所选的Jquery造成DropDownList的不更新。

I was using the Chosen Jquery which caused the dropdownlist to not update.

这是HTML：

<select name="ctl00$BodyPlaceHolder$ddl1" id="ddl1" class="chose-select le">
    <option value="Select a State">Select a State</option>
    <option value="Alabama">AL</option>
    <option value="Alaska">AK</option>
    <option value="Arizona">AZ</option>
</select>

JavaScript代码在选定的索引设置为0：

JavaScript which sets the selected index to 0:

function setSelectedIndex(dropdownlist, selVal) {
    var ddl1 = document.getElementById(dropdownlist);
    if (selVal < ddl1.selectedIndex) {
        ddl1.selectedIndex = selVal;

        $(ddl1).val(0).trigger('chosen:updated');
    }
}

这是卓有成效的。

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