当我从数据库中检索时，如何验证下拉列表 [英] how to validate dropdownlist, when i retrived from database

问题描述

当我从databse中获取数据时，如何验证drowndownlist.

例如，下拉列表名称为City.如果用户未选择城市均值
然后我要在替代框中显示msg像(选择城市")

how to validate drowndownlist, when i retived data from databse.

for example dropdownlist name is City.if user does not select a city mean
then i want display msg like("slect a city) in alter box

推荐答案

绑定DropDownList后插入一个请选择项目:

After binding your DropDownList insert a please select item:

myDDL.Items.Insert(0, new ListItem("Please Select A City", "0"));

然后，在保存按钮的单击事件上，只需检查您的DropDownLists选定值:

Then, on your save button''s click event you just check your DropDownLists selected value:

if (myDDL.SelectedValue == "0")
{
    myErrorLabel.Text = "Please Select a City";
    return;
}

//Save info to database here

尝试类似的方法:

Try something like this:

<asp:requiredfieldvalidator id="rfvCity" runat="server" controltovalidate="ddlCity" display="Dynamic" enableclientscript="true" errormessage="Please Select a City" forecolor="Red" initialvalue="Select a City..." xmlns:asp="#unknown">*&nbsp;</asp:requiredfieldvalidator>

您需要在页面上的某处添加<asp:validationsummary id="valSummary" runat="server" forecolor="Red" xmlns:asp="#unknown" />才能显示错误消息.

You''ll need to add <asp:validationsummary id="valSummary" runat="server" forecolor="Red" xmlns:asp="#unknown" /> somewhere on the page to display the error message.

验证此问题的3种方法

1.使用服务器端代码(C#，VB)

3 way to validate this problem

1. Using Server Side code (C#, VB)

if(dropdownList1.SelectedValue=="")
{
   lblMessage.Text="Please Select Your City.";
   return;
}

2.使用RequiredFieldValidator

2. Using RequiredFieldValidator

<asp:DropDownList ID="DropDownList1" runat="server">
    <asp:ListItem></asp:ListItem>
    <asp:ListItem Value="Male"></asp:ListItem>
    <asp:ListItem>Female</asp:ListItem>
</asp:DropDownList>


<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"

    ErrorMessage="Please Select City" ControlToValidate="DropDownList1"

    ForeColor="Red"></asp:RequiredFieldValidator>

3.使用JavaScript

3. Using JavaScript

<script type="text/javascript">
    function CheckDropDownList() {
        if (document.getElementById('DropDownList1').selectedIndex = "0")
            alert('Please Select City');
    }
</script>

<asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="CheckDropDownList()" />

了解验证控制，请访问
http://msdn.microsoft.com/en-us/library/aa479013.aspx [ ^ ]



谢谢

learn about validation control please visit
http://msdn.microsoft.com/en-us/library/aa479013.aspx[^]



Thanks

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