Скачать или смотреть Solving the ModelState Validation Issue for Multiple Models in ASP.NET MVC

Learn how to effectively manage login and registration forms using multiple models in a single view with proper validation in ASP.NET MVC.
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This video is based on the question https://stackoverflow.com/q/66139961/ asked by the user 'Shane' ( https://stackoverflow.com/u/5971071/ ) and on the answer https://stackoverflow.com/a/66141930/ provided by the user 'Shane' ( https://stackoverflow.com/u/5971071/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the ModelState Validation Issue for Multiple Models in ASP.NET MVC

In the world of ASP.NET MVC, handling multiple models in a single view can often lead to complex issues, especially when it comes to validation. If you find that your ModelState is always valid even when you expect it to fail, you're not alone. In this guide, we will dive deep into the problem: validating login and registration forms when both share the same view and how to troubleshoot it effectively.

The Problem

Many developers encounter a scenario where they have an MVC 5 application that allows users to either log in or register from the same view. Despite having proper validation attributes set up in their model classes, the ModelState may not reflect the expected results. More specifically, when fields are left empty and the user tries to log in, they receive a null reference, and the ModelState reports as valid.

Here's a brief outline of the models we're dealing with:

LoginModel

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

RegisterModel

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

The Solution

After some investigation, a solution was discovered that involves modifying the ViewModel and adjusting how data is handled in the controller actions. Let’s break it down step by step.

Step 1: Modify the ViewModel

Add the fields defined in the LoginModel and RegisterModel directly to the ViewModelVM so that they can be accessed easily during binding.

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

Step 2: Update the View

Next, update the view by making changes to how each input field is handled. We're going to remove the bindings to loginModel and registerModel for the validation messages.

For instance, replace:

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

with:

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

Step 3: Adjust the Controller Actions

The final step is in the controller. Instead of passing the entire ViewModelVM to the LoginSubmit action, you should pass only the LoginModel and construct the ViewModel within the method itself.

Here’s the modified LoginSubmit action:

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

Conclusion

By modifying your ViewModel and adjusting how data is processed in the controller, you can resolve the issue of persistent ModelState validity that frustrates so many developers working with multiple models in a single view. Embrace these changes, and you’ll find that your application becomes much more predictable and user-friendly. Happy coding!