问题
This is how i am loading on page load state and city dropdown:
My Controller method:
This is the first method which is calling when page is loaded.
public ActionResult Index()
{
var states = GetStates();
var cities = Enumerable.Empty<SelectListItem>();
ViewBag.States = states;
ViewBag.Cities = cities;
}
private IEnumerable<SelectListItem> GetStates()
{
using (var db = new DataEntities())
{
return db.States.Select(d => new SelectListItem { Text = d.StateName, Value =d.Id.ToString() });
}
}
[HttpGet]
public ActionResult GetCities(int id)
{
using (var db = new DataEntities())
{
var data = db.Cities.Where(d=>d.StateId==id).Select(d => new { Text = d.CityName, Value = d.Id }).ToList();
return Json(data, JsonRequestBehavior.AllowGet);
}
}
My View:
IEnumerable<SelectListItem> States = ViewBag.States;
IEnumerable<SelectListItem> Cities = ViewBag.Cities;
@Html.DropDownList(\"State\", States, \"Select State\", new { onchange=\"loadCities(this)\"})
@Html.DropDownListFor(m => m.CityId, Cities, \"Select City\", new { id=\"ddlCity\"})
function loadCities(obj) {
$.ajax({
url: \"/Home/GetCities\",
data: { id: $(obj).val() },
contentType:\"application/json\",
success:function(responce){
var html = \'<option value=\"0\">Select City</option>\';
$(responce).each(function () {
html += \'<option value=\"\'+this.Value+\'\">\'+this.Text+\'</option>\'
});
$(\"#ddlCity\").html(html);
}
});
}
Any better way then this to load state and city dropdown?
public class HomeController : Controller
{
public ActionResult Index(int id=0)
{
Person model = null;
var states = GetStates().ToList();
var cities = Enumerable.Empty<SelectListItem>();
if (id > 0)
{
using (var db = new DataEntities())
{
model = db.People.Include(\"City\").FirstOrDefault(d => d.Id == id);
if (model == null)
model = new Person();
else
{
states.First(d => d.Value == model.City.StateId.ToString()).Selected = true;
cities = db.Cities.Where(d => d.StateId == model.City.StateId).ToList().Select(d => new SelectListItem { Text = d.CityName,Value=d.Id.ToString(),Selected=d.Id==model.CityId });
}
}
}
else
{
model = new Person();
}
ViewBag.States = states;
ViewBag.Cities = cities;
ViewBag.Persons = GetPersons();
return View(model);
}
[HttpGet]
public ActionResult GetCities(int id)
{
using (var db = new DataEntities())
{
var data = db.Cities.Where(d=>d.StateId==id).Select(d => new { Text = d.CityName, Value = d.Id }).ToList();
return Json(data, JsonRequestBehavior.AllowGet);
}
}
public ActionResult SavePersonDetail([Bind(Exclude = \"Id\")] Person model)
{
// var employeeDal= new Emploee();
//employee.firstname=model.
if (ModelState.IsValid)
{
var Id = model.Id;
int.TryParse(Request[\"Id\"], out Id);
using (var db = new DataEntities())
{
if (Id > 0)
{
var person = db.People.FirstOrDefault(d => d.Id == Id);
if (person != null)
{
model.Id = Id;
db.People.ApplyCurrentValues(model);
}
}
else
{
db.People.AddObject(model);
}
db.SaveChanges();
}
}
if (!Request.IsAjaxRequest())
{
ViewBag.States = GetStates();
ViewBag.Persons = GetPersons();
ViewBag.Cities = Enumerable.Empty<SelectListItem>();
return View(\"Index\");
}
else
{
return PartialView(\"_personDetail\",GetPersons());
}
}
public ActionResult Delete(int id)
{
using (var db = new DataEntities())
{
var model = db.People.FirstOrDefault(d => d.Id == id);
if (model != null)
{
db.People.DeleteObject(model);
db.SaveChanges();
}
}
if (Request.IsAjaxRequest())
{
return Content(id.ToString());
}
else
{
ViewBag.States = GetStates();
ViewBag.Persons = GetPersons();
ViewBag.Cities = Enumerable.Empty<SelectListItem>();
return View(\"Index\");
}
}
private IEnumerable<SelectListItem> GetStates()
{
using (var db = new DataEntities())
{
return db.States.ToList().Select(d => new SelectListItem { Text = d.StateName, Value =d.Id.ToString() });
}
}
private IEnumerable<Person> GetPersons()
{
using (var db = new DataEntities())
{
return db.People.Include(\"City\").Include(\"City.State\").ToList();
}
}
public ActionResult HomeAjax()
{
ViewBag.States = GetStates();
ViewBag.Cities = Enumerable.Empty<SelectListItem>();
using (var db = new DataEntities())
{
var data = db.States.Include(\"Cities\").Select(d => new { Id = d.Id, Name = d.StateName, Cities = d.Cities.Select(x => new { Id=x.Id,Name=x.CityName}) }).ToList();
ViewBag.CityStateJson = new System.Web.Script.Serialization.JavaScriptSerializer().Serialize(data);
}
ViewBag.Persons = GetPersons();
return View();
}
}
@model IEnumerable<Person>
<div>
<table>
<tr>
<th>
First Name
</th>
<th>
Last Name
</th>
<th>
Email
</th>
<th>
City
</th>
<th>
State
</th>
<th>
Edit
</th>
</tr>
@if (Model.Count() == 0)
{
<tr>
<td colspan=\"6\">
<h3>No data available</h3>
</td>
</tr>
}
else {
foreach (var item in Model) {
<tr data-id=\"@item.Id\">
<td data-id=\"fn\">@item.FirstName</td>
<td data-id=\"ln\">@item.LastName</td>
<td data-id=\"email\">@item.Email</td>
<td data-id=\"cn\">@item.CityName<input type=\"hidden\" value=\"@item.CityId\" /></td>
<td>@item.StateName</td>
<td>
@if (ViewBag.Title == \"Home Ajax\" || Request.IsAjaxRequest())
{
<a href=\"javascript:void(0);\" onclick=\"Edit(this,@item.Id);\">Update</a>
<span>@Ajax.ActionLink(\"Delete\", \"Delete\", new { id = item.Id }, new AjaxOptions {OnSuccess=\"deleteSuccess\",OnBegin=\"showLoader\",OnComplete=\"hideLoader\" })</span>
}
else {
<span>@Html.ActionLink(\"Update\", \"Index\", new { id = item.Id })</span>
<span>@Html.ActionLink(\"Delete\", \"Delete\", new { id = item.Id })</span>
}
</td>
</tr>
}
}
</table>
</div>
@model Person
@{
ViewBag.Title = \"Home Ajax\";
IEnumerable<Person> persons = ViewBag.Persons;
IEnumerable<SelectListItem> States = ViewBag.States;
IEnumerable<SelectListItem> Cities = ViewBag.Cities;
IEnumerable<State> fullStates=ViewBag.CityStates;
}
@section featured {
<section class=\"featured\">
<div class=\"content-wrapper\">
<hgroup class=\"title\">
<h1>@ViewBag.Title.</h1>
</hgroup>
</div>
</section>
}
@section styles{
<style type=\"text/css\">
td,th {
border:1px solid;
padding:5px 10px;
}
select {
padding:5px 2px;
width:310px;
font-size:16px;
}
</style>
}
@section scripts{
@Scripts.Render(\"~/bundles/jqueryval\")
<script type=\"text/javascript\">
var jsonArray = @Html.Raw(ViewBag.CityStateJson)
function clearValues() {
$(\"input[type=\'text\'],select\").val(\'\');
$(\"input[type=\'hidden\'][name=\'Id\']\").val(0);
}
function loadCities(obj) {
for (var i = 0; i < jsonArray.length; i++) {
if (jsonArray[i].Id == parseInt($(obj).val())) {
fillCity(jsonArray[i].Cities);
break;
}
}
}
function Edit(obj, Id) {
// alert(\"hi\")
$(\"input[type=\'hidden\'][name=\'Id\']\").val(Id);
var tr = $(obj).closest(\"tr\");
$(\"#txtfirstName\").val($(\"td[data-id=\'fn\']\", tr).text().trim());
$(\"#txtlastName\").val($(\"td[data-id=\'ln\']\", tr).text().trim());
$(\"#txtemail\").val($(\"td[data-id=\'email\']\", tr).text().trim());
var city = $(\"td[data-id=\'cn\'] input[type=\'hidden\']\", tr).val();
var state;
for (var i = 0; i < jsonArray.length; i++) {
for (var j = 0; j < jsonArray[i].Cities.length; j++) {
if (jsonArray[i].Cities[j].Id == parseInt(city)) {
state = jsonArray[i].Id;
break;
}
}
if (state) {
fillCity(jsonArray[i].Cities);
break;
}
}
$(\"#ddlState\").val(state);
$(\"#ddlCity\").val(city);
}
function fillCity(obj) {
var html = \'<option value=\"0\">Select City</option>\';
$(obj).each(function () {
html += \'<option value=\"\' + this.Id + \'\">\' + this.Name + \'</option>\'
});
$(\"#ddlCity\").html(html);
}
function deleteSuccess(responce) {
alert(\"record deleted successfully\");
$(\"tr[data-id=\'\" + responce + \"\']\").remove();
}
function insertSuccess() {
alert(\"Record saved successfully\");
clearValues();
}
function showLoader() {
$(\"#overlay\").show();
}
function hideLoader() {
$(\"#overlay\").hide();
}
</script>
}
<h3>Add Personal Detail</h3>
@using (Ajax.BeginForm(\"SavePersonDetail\", \"Home\", new AjaxOptions { HttpMethod = \"POST\", UpdateTargetId = \"personList\" ,OnSuccess=\"insertSuccess\",OnBegin=\"showLoader\",OnComplete=\"hideLoader\"}))
{
@Html.HiddenFor(m => m.Id);
<ol class=\"round\">
<li>
@Html.LabelFor(m => m.FirstName)
@Html.TextBoxFor(m => m.FirstName, new { id = \"txtfirstName\" })
@Html.ValidationMessageFor(m => m.FirstName)
</li>
<li>
@Html.LabelFor(m => m.LastName)
@Html.TextBoxFor(m => m.LastName, new { id = \"txtlastName\" })
@Html.ValidationMessageFor(m => m.LastName)
</li>
<li>
@Html.LabelFor(m => m.Email)
@Html.TextBoxFor(m => m.Email, new { id = \"txtemail\" })
@Html.ValidationMessageFor(m => m.Email)
</li>
<li>
@Html.Label(\"State\")
@Html.DropDownList(\"State\", States, \"Select State\", new { onchange = \"loadCities(this)\", id = \"ddlState\" })
</li>
<li>
@Html.LabelFor(m => m.CityId)
@Html.DropDownListFor(m => m.CityId, Cities, \"Select City\", new { id = \"ddlCity\" })
@Html.ValidationMessageFor(m => m.CityId)
</li>
</ol>
<input type=\"submit\" value=\"Save\" />
<input type=\"button\" value=\"Cancel\" onclick=\"clearValues();\"/>
}
<h2>
Person List
</h2>
<div style=\"position:fixed;text-align:center;top:0;bottom:0;left:0;right:0;z-index:10;background-color:black;opacity:0.6;display:none;\" id=\"overlay\">
<img style=\"position:relative;top:370px\" src=\"~/Images/ajax-loader.gif\" />
</div>
<div id=\"personList\">
@Html.Partial(\"_personDetail\", persons)
</div>
回答1:
You approach using ajax is fine although I would recommend a few better practices including using a view model with properties for StateID, CityID StateList and CityList, and using Unobtrusive JavaScript rather than polluting you markup with behavior, and generating the first ("please select") option with a null value rather than 0 so it can be used with the [Required] attribute
HTML
@Html.DropDownList(m => m.StateID, States, "Select State") // remove the onchange
@Html.DropDownListFor(m => m.CityID, Cities, "Select City") // why change the default ID?
SCRIPT
var url = '@Url.Action("GetCities", "Home")'; // use the helper (dont hard code)
var cities = $('#CityID'); // cache the element
$('#StateID').change(function() {
$.getJSON(url, { id: $(this).val() }, function(response) {
// clear and add default (null) option
cities.empty().append($('<option></option>').val('').text('Please select'));
$.each(response, function(index, item) {
cities.append($('<option></option>').val(item.Value).text(item.Text));
});
});
});
If you were rendering multiple items (say you were asking the user to select their last 10 cities they visited), you can cache the result of the first call to avoid repeated calls where their selections may include cities from the same state.
var cache = {};
$('#StateID').change(function() {
var selectedState = $(this).val();
if (cache[selectedState]) {
// render the options from the cache
} else {
$.getJSON(url, { id: selectedState }, function(response) {
// add to cache
cache[selectedState] = response;
.....
});
}
});
Finally, in response to your comments regarding doing it without ajax, you can pass all the cities to the view and assign them to a javascript array. I would only recommend this if you have a few countries, each with a few cities. Its a matter of balancing the slight extra initial load time vs the slight delay in making the ajax call.
In the controller
model.CityList = db.Cities.Select(d => new { City = d.CountryID, Text = d.CityName, Value = d.Id }).ToList();
In the view (script)
// assign all cities to javascript array
var allCities= JSON.parse('@Html.Raw(Json.Encode(Model.CityList))');
$('#StateID').change(function() {
var selectedState = $(this).val();
var cities = $.grep(allCities, function(item, index) {
return item.CountryID == selectedState;
});
// build options based on value of cities
});
回答2:
This is a correct approach, but you can simplify your javascript:
function loadCities(obj) {
$.getJSON("/Home/GetCities", function (data) {
var html = '<option value="0">Select City</option>';
$(data).each(function () {
html += '<option value="'+this.Value+'">'+this.Text+'</option>'
});
$("#ddlCity").html(html);
});
}
Further possible simplification: Add the default item (Select City) server-side, so your javascript will be smaller.
回答3:
Here's how I'd do it without the page refresh, assuming the list of cities isn't too long.
I'm assuming you can create a GetStatesAndCities method to return a Dictionary.
public ActionResult Index()
{
Dictionary<string, List<String>> statesAndCities = GetStatesAndCities();
ViewBag.StatesAndCities = Json(statesAndCities);
}
Then in the view:
var states = JSON.parse(@ViewBag.StatesAndCities);
function loadCities(obj) {
var cities = states[$(obj).val()];
var html = '<option value="0">Select City</option>';
$(cities).each(function () {
html += '<option value="'+this.Value+'">'+this.Text+'</option>'
});
$("#ddlCity").html(html);
}
This way when the state is changed the cities field with update immediately with no need for callback.
回答4:
disclaimer: This is not a code answer, there are plenty other answers.
I think best way to keep yourself happy to seperate UI pages from data => turn them into API calls:
- /GetCities
- /GetStates
Now you can simply leave the select's empty on Razor rendering the page. And use a Jquery/Bootstrap plugin to create an AJAX select box.
This way when the user stops typing his search, this search string can than be send with the AJAX call (eg: /GetStates?search=test) and then a small result set can be send back to the website.
This gives:
- Better separation in serveside code
- Better User eXperience.
- Smaller page loads (since you no longer send all the options to user when he requests the page, only when he opens the select box).
回答5:
How about using Knockout?
Knockout is a JavaScript library that helps you to create rich, responsive display and editor user interfaces with a clean underlying data model
You have to use ajax for your cities. But with knockout you dont need to write
var html = '<option value="0">Select City</option>';
$(responce).each(function () {
html += '<option value="'+this.Value+'">'+this.Text+'</option>'});
$("#ddlCity").html(html);
in your javascript.Knockout makes it simple.
You can simply write:
function CityModel() {
var self = this; // that means this CityModel
self.cities = ko.observableArray([]);
self.getCities = function () {
$.ajax({
url: "/Home/GetCities",
data: { id: $(obj).val() },
contentType: "application/json",
success: self.cities
});
}
}
ko.applyBindings(new CityModel());
thats all. But you have to bind your data into html elements.
Instead of using :
@Html.DropDownListFor(m => m.CityId, Cities, "Select City", new { id="ddlCity"})
You can use:
<select data-bind="options:cities,optionsValue:"Id",optionsText:"CityName",optionsCaption:"Select City""></select>
or you can mix razor and knockout:
@Html.DropDownListFor(m => m.CityId, Cities, "Select City", new { id="ddlCity",data_bind:"options:cities,optionsValue:\"Id\",optionsText:\"CityName\""})
One more thing you have to call GetCities when State changes, you can :
@Html.DropDownList("State", States, "Select State", new {data_bind:"event:\"change\":\"$root.GetCities\""})
Dont be scare with \"\" things this because " is an escape character and we have to say to razor i want to use " by using \ before it.
You can find more info about knockout :Knockout
And mixing with razor: Razor and Knockout
Ps: yes using knockout is suspend us from Razor and Mvc. You have to write another ViewModel . But like this situations ko is helpful. Mixing razor and knockout is another option for you.
来源：https://stackoverflow.com/questions/28627421/better-way-to-load-2-dropdown-in-mvc