asp.net的下拉列表验证 [英] drop down list validation for asp.net

问题描述

用户忘记在下拉列表中选择一个值，因此如果他们忘记选择，我需要给出警报消息，怎么办?我不知道请帮助我

in vb.net web project, user forget to select a value in dropdownlist, so i need to give alert message if they forget to select, how to do? i don''t know help me please

推荐答案

您好，您可以实现一个简单的JavaScript验证功能，并在Button的OnClientClick方法上调用它.
下面是代码.

aspx代码

Hi, you can implement a simple JavaScript validation function and call it on Button''s OnClientClick method.
Below is the code.

aspx code

<asp:DropDownList ID="dropDown1" runat="server" AutoPostBack="false">
    <asp:ListItem Text="None" />
    <asp:ListItem Text="text1" />
    <asp:ListItem Text="text2" />
    <asp:ListItem Text="text3" />
</asp:DropDownList>

<asp:Button ID="Button1" runat="server" Text="Submit" OnClientClick="javascript:return ValidateDropDown();" />

JavaScript代码

JavaScript Code

function ValidateDropDown() {
    var cmbID = "<%=dropDown1.ClientID %>";
    if (document.getElementById(cmbID).selectedIndex == 0) {
        alert("Please select a Value");
        return false;
    }
    return true;
}

希望这能解决您的问题.

Hope this will solve your problem..

<asp:DropDownList ID="dropDown1" runat="server" AutoPostBack="false">
    <asp:ListItem Text="None" selected="True"/>
    <asp:ListItem Text="text1" />
    <asp:ListItem Text="text2" />
    <asp:ListItem Text="text3" />
</asp:DropDownList>

<asp:requiredfieldvalidator id="RequiredFieldValidator1" runat="server" text="*" controltovalidate="dropDown1" errormessage="Please Select Category" initialvalue="None" xmlns:asp="#unknown"></asp:requiredfieldvalidator>


<asp:Button ID="Button1" runat="server" Text="Submit"  />

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