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How Can I Efficiently Load Dependent Dropdowns (State and City) in MVC Using Unobtrusive JavaScript?
How Can I Efficiently Load Dependent Dropdowns (State and City) in MVC Using Unobtrusive JavaScript?
Jan 28, 2025 pm 06:26 PM
Traditionally, loading the state and urban drop -down menu in the MVC application requires the combination of the controller operation and the JavaScript code. Although this method is effective, it may be tedious and easy to make mistakes. Let us explore a more efficient and more powerful way to deal with this task.
Using view models and non -invasive javascript
Instead of coding the drop -down menu in the view, it is better to introduce a view model to contain all the necessary data. In addition, we will use non -invasive JavaScript to enhance user experience without pollution marking.
View model
Controller operation
public class PersonViewModel
{
public int StateID { get; set; }
public int CityID { get; set; }
public List<SelectListItem> States { get; set; }
public List<SelectListItem> Cities { get; set; }
} In the controller operation, we will prepare the view model and pass it to the view. <圖> View
In the view, we will use the
public ActionResult Index()
{
var states = GetStates().Select(s => new SelectListItem { Value = s.Id.ToString(), Text = s.Name }).ToList();
var cities = GetCities().Select(c => new SelectListItem { Value = c.Id.ToString(), Text = c.Name }).ToList();
var model = new PersonViewModel
{
States = states,
Cities = cities
};
return View(model);
} helper to present the drop -down menu. <侵> Non -invasive JavaScript
@Html.DropDownList Using jQuery, we can enhance the behavior of the state drop -down menu and dynamically load the city.
@model PersonViewModel ... @Html.DropDownListFor(m => m.StateID, Model.States, "請選擇州") @Html.DropDownListFor(m => m.CityID, Model.Cities, "請選擇城市") ...
<勢> advantages
This method provides the following advantages:
$(document).ready(function() {
$("#StateID").change(function() {
var stateId = $(this).val();
$.ajax({
url: '@Url.Action("GetCities", "Home")',
data: { stateId: stateId },
success: function(response) {
var citiesDropdown = $('#CityID');
citiesDropdown.empty();
citiesDropdown.append($("<option></option>").attr("value", "").text("請選擇城市")); // 添加默認選項
$.each(response, function(index, city) {
citiesDropdown.append($("<option></option>").attr("value", city.Id).text(city.Name));
});
}
});
});
}); By eliminating the operation of multiple controllers, the complexity of the code is reduced. Due to the separation of the focus between view models, controllers and views, it improves maintenance.
By improving the user experience by loading cities in the selected state.Essable requests only when necessary to reduce the server load.
- Note: The above code clips assume that
- and methods have existed and returned appropriate data, and
- and objects have
- and properties. The use of
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