如何验证下拉列表 [英] How to validate dropdown list

问题描述

我有下拉列表和子下拉列表如果我在主下拉列表中选择水果选项子选项将显示多选验证在保存选项中选择的任何一个。

告诉我任何想法谢谢。



我的尝试：



< asp： DropDownList ID =DropDownList4class =form-controlrunat =server>

< asp：ListItem Value =1> - SELECT -

< asp：ListItem Value =2>水果

< asp：ListItem Value =3> veg









< asp：ListBox ID =Select49SelectionMode =Multiplerunat =server>

< asp：ListItem Value =1> 4

< asp：ListItem Value =2> 8

< asp：ListItem Value =3> 12

< asp：ListItem Value =4> 16

解决方案

用于验证



< pre lang =HTML> < asp：button id = btnSave text = 保存 onclientclick = 返回ValidateFun（）; runat = server onclick = btnSave_Click xmlns：asp = ＃unknown / >

Javascript：

< script> 
 var ValidateFun = function（）
 {
 var listbox = document.getElementById（'<％= Select49.ClientID％>'）; 
 var count = listbox.selectedOptions.length; 
 if（count == 0）
 {alert（'Please select !!'）;返回false; } 
返回true; 
} 
< / script> 
 

i have dropdown list and also sub drop down list if i select fruit select in main dropdown list sub option will display that is multi select validate any one selected in save option.
tell me any idea thanks regards

What I have tried:

<asp:DropDownList ID="DropDownList4" class="form-control" runat="server">
<asp:ListItem Value="1">--SELECT--
<asp:ListItem Value="2">fruit
<asp:ListItem Value="3">veg




<asp:ListBox ID="Select49" SelectionMode="Multiple" runat="server">
<asp:ListItem Value="1"> 4
<asp:ListItem Value="2">8
<asp:ListItem Value="3">12
<asp:ListItem Value="4">16

解决方案

For validation

<asp:button id="btnSave" text="Save" onclientclick="return ValidateFun();" runat="server" onclick="btnSave_Click" xmlns:asp="#unknown" />

Javascript:

<script>
    var ValidateFun = function ()
    {
        var listbox = document.getElementById('<%= Select49.ClientID%>');
        var count = listbox.selectedOptions.length;
        if (count == 0)
        { alert('Please select !!'); return false; }
        return true;
    }
</script>

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