Member Avatar for bala24

Hi,
I need to do the usual i.e design a form to get user registration details.
I need to allow him to select his country ,state city but i figure making three separate postbacks would greatly reduce the performance.

Alternatively i was planning to fetch the whole data at client and then sort through it by querying it somehow.
Is it possible??How??

Thanks in advance

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Dani AI

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raised the right concern: three full page postbacks for country → state → city will slow the UI. Two practical patterns work well: preload the entire dataset to the browser and filter with JavaScript (fast for small data), or request dependent lists on demand with lightweight AJAX/web‑methods (scales better). 's question about the control is relevant — any standard <select> (DropDownList) can be driven client‑side; avoid server postbacks on change.

A minimal, robust pattern for ASP.NET WebForms (VB) is a Shared WebMethod that returns a small JSON array (id/name) and a short jQuery AJAX call to populate the child dropdown. The WebMethod must be Shared and marked with <WebMethod>. jQuery will receive the data in response.d when calling page methods.

Code samples:

<System.Web.Services.WebMethod()> _
Public Shared Function GetStates(countryId As Integer) As List(Of Dictionary(Of String, Object))
    ' server: query DB, build list of { "Id"=x, "Name"="..." } and return
End Function
// client: POST JSON to /Page.aspx/GetStates, fill dropdown from response.d
$.ajax({
  type: "POST",
  url: "Register.aspx/GetStates",
  data: JSON.stringify({ countryId: id }),
  contentType: "application/json; charset=utf-8",
  dataType: "json",
  success: function(r){ /* populate select with r.d */ }
});

Practical tips: return only id+name to keep payload tiny, enable gzip on the site, cache server results, and consider localStorage for repeat visits. Avoid UpdatePanel for frequent cascading calls — its viewstate overhead is heavier than a small JSON AJAX call.

Member Avatar for kapil.goyal

which control u r using to bind data.

Member Avatar for bala24

I am using a datareader to fetch the data and then a drop down to show the values.

Does that help??

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