How to Create Cascading DropDownLists Using ASP.Net MVC

Learn how to implement cascading dropdown lists in ASP.Net MVC with a step-by-step guide that includes controller, view, and JavaScript code snippets.
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How to Create Cascading DropDownLists Using ASP.Net MVC

Cascading dropdown lists are an effective way of allowing users to make a dependent selection in a web application. This is especially useful in scenarios where the choices in one dropdown affect the available choices in another. In this guide, we will walk through how to create cascading dropdown lists using ASP.Net MVC, focusing on how to populate a "state" dropdown based on the selection made in a "country" dropdown.

Understanding the Problem

Imagine you have a form that requires users to select a country and then choose a related state from another dropdown. If the first dropdown (country) is selected, the second dropdown (state) should automatically update to reflect only the states relevant to the selected country. However, users may face issues where after making their selection, the dropdowns do not populate correctly or the form does not redirect as expected.

Here’s a common scenario:

The initial dropdown for countries populates with the correct data.

The dropdown for states remains empty regardless of the country selection.

Solution Breakdown

To solve this problem, we will need to implement the following components:

1. Controller Logic

The first step is to set up our controller in ASP.Net MVC.

[[See Video to Reveal this Text or Code Snippet]]

In this code:

We are retrieving a list of countries from the database and populating a dropdown list via ViewBag.

2. JSON Method for States

Next, we create a method to get the states based on the selected country.

[[See Video to Reveal this Text or Code Snippet]]

Here:

We execute a SQL query to fetch states that correspond to the selected country and return the results in JSON format.

3. View Setup

Now that our controller is set up, let’s move to the view where we include the dropdowns and the JavaScript needed to handle the change event.

[[See Video to Reveal this Text or Code Snippet]]

4. JavaScript for AJAX Call

Finally, we implement the JavaScript code that triggers an AJAX call when the country dropdown changes.

[[See Video to Reveal this Text or Code Snippet]]

In this JavaScript:

We monitor the change event on the country dropdown and initiate an AJAX request to fetch states dynamically.

The received states are then populated in the state dropdown.

Conclusion

By following these steps, you can successfully create a cascading dropdown list in your ASP.Net MVC application. This implementation enhances user experience by reducing the need for users to scroll through irrelevant options. If you have any questions or run into issues while implementing this, feel free to ask for help!