ASP.net: Everything is fine, but Autopostback is not working in cascading dropdownlist. Why?
Check the following code:
<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub ddlState_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
ddlCity.Items.Clear()
ddlCity.Items.Add("Select City")
Select Case ddlState.SelectedValue
Case "MS"
ddlCity.Items.Add("Aurangabad")
ddlCity.Items.Add("Mumbai")
ddlCity.Items.Add("Pune")
Case "GU"
ddlCity.Items.Add("Vadodara")
ddlCity.Items.Add("Surat")
Case "KA"
ddlCity.Items.Add("Bangalore")
Case "AP"
ddlCity.Items.Add("Hyderabad")
End Select
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
State:
<asp:DropDownList ID="ddlState" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlState_SelectedIndexChanged">
<asp:ListItem Value="">Select State</asp:ListItem>
<asp:ListItem Value="MS">Maharashtra</asp:ListItem>
<asp:ListItem Value="GU">Gujrat</asp:ListItem>
<asp:ListItem Value="KA">Karnataka</asp:ListItem>
<asp:ListItem Value="AP">Andhra Pradesh</asp:ListItem>
</asp:DropDownList>
City:
<asp:DropDownList ID="ddlCity" runat="server">
</asp:DropDownList>
<asp:Button ID="submit" runat="server" Text="Button" />
</form>
</body>
</html>
Answer:
There is some bug with asp.net when you use a button with Id="submit", it cancels Autopostback. Simply change Id="btnSubmit", Autopostback will start working.
<asp:Button ID="submit" runat="server" Text="Button" />
Change to
<asp:Button ID="btnSubmit" runat="server" Text="Button" />
Hope this helps you and saves your time.
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