Javascript 使用vb在asp.net中限制列表框中的项目选择
我想使用vb限制asp.net中列表框中的项目选择数量。我试着用javascript。但是,不起作用。需要帮助吗Javascript 使用vb在asp.net中限制列表框中的项目选择,javascript,asp.net,Javascript,Asp.net,我想使用vb限制asp.net中列表框中的项目选择数量。我试着用javascript。但是,不起作用。需要帮助吗 <asp:ListBox ID="lbprefferedlocation" runat="server" DataSourceID="locations" DataTextField="City_Name" OnSelectedIndexChanged="chkCount(this)" DataValueField="City_Name" Se
<asp:ListBox ID="lbprefferedlocation" runat="server" DataSourceID="locations"
DataTextField="City_Name" OnSelectedIndexChanged="chkCount(this)" DataValueField="City_Name" SelectionMode="Multiple"></asp:ListBox>
<asp:HiddenField ID="hiddenChkCount" runat="server" />
<asp:SqlDataSource ID="locations" runat="server"
ConnectionString="<%$ ConnectionStrings:JPConnString %>"
SelectCommand="SELECT [City_Name] FROM [State_Info]"></asp:SqlDataSource>
function chkCount(obj)
{
if(obj.checked==true)
{
if( document.getElementById( '<%=hiddenChkCount.ClientID %>' ).value >= 5 )
{
alert('You cannot select more than 5 items.');
obj.checked=false;
}
else
{
document.getElementById( '<%=hiddenChkCount.ClientID %>' ).value = parseInt( document.getElementById( '<%=hiddenChkCount.ClientID %>' ).value ) + 1;
}
}
else
{
document.getElementById( '<%=hiddenChkCount.ClientID %>' ).value = parseInt( document.getElementById( '<%=hiddenChkCount.ClientID %>' ).value) - 1;
}
}
功能chkCount(obj)
{
如果(对象检查==真)
{
if(document.getElementById(“”).value>=5)
{
警报('您不能选择超过5项');
检查对象=错误;
}
其他的
{
document.getElementById(“”).value=parseInt(document.getElementById(“”).value)+1;
}
}
其他的
{
document.getElementById(“”).value=parseInt(document.getElementById(“”).value)-1;
}
}
您可以使用CustomValidator
:
<asp:CustomValidator ID="CV_CheckLocationCount" runat="server"
ValidateEmptyText="true"
ClientValidationFunction="CheckLocationCount"
OnServerValidate="CheckLocationCount"
ControlToValidate="lbprefferedlocation"
EnableClientScript="true"
ErrorMessage="Select at least one and at most 5 locations"
ValidationGroup="VG_SAVE">*
</asp:CustomValidator>
function CheckLocationCount(sender, args){
var count=$('#<%=lbprefferedlocation.ClientID %> option:selected').length;
args.IsValid = count > 0 && count <= 5;
}
*
函数CheckLocationCount(发送方,参数){
变量计数=$('#选项:选定')。长度;
args.IsValid=count>0&&count“CheckLocationCount”不是member@coders_zone:可能是因为您没有在服务器端提供CheckLocationCount
。您应该始终在客户端和服务器端进行验证。那么,我应该在服务器端写些什么…??@coders\u zone:受保护的void CheckLocationCounton(对象源,ServerValidateEventArgs args){args.IsValid=lbpreferedLocation.Items.Cast().Where(i=>i.Selected.Count()@coders_zone:args.IsValid=lbpreferedLocation.Items.Cast(属于ListItem)().Where(函数(i)i.Selected.Count())
function validateListBoxSelectionCount(listbox, minSelected, maxSelected){
var selected=0;
if(listbox != null){
for (var i=0; i<listbox.length; i++){
if(listbox.options[i].selected){
selected++;
if(selected>maxSelected)break;
}
}
}
return (selected >= minSelected && selected <= maxSelected);
}
var listBox = document.getElementById("<%=lbprefferedlocation.ClientID %>");
args.IsValid = validateListBoxSelectionCount(listBox, 1, 5);