Resolving the Issue of ASP.NET Core MVC Value Passing from View to Controller

Discover how to fix the issue of `null` value being received in the controller when using ASP.NET Core MVC for passing values from view.
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The Problem of Passing Values in ASP.NET Core MVC: A Common Pitfall

Working with ASP.NET Core MVC, developers often encounter various challenges when dealing with data transfer between views and controllers. One such common issue arises when a view fails to pass values correctly to its corresponding controller action.

In this article, we'll explore a specific scenario where a developer is attempting to delete a record from a database via a form in a view, but encounters an issue where the ID value is not being sent to the controller. Instead, the controller receives a null value, which prevents the delete operation from executing as intended.

Understanding the Challenge

In the provided setup:

The view is correctly populated and displays the necessary details.

A button labeled "Delete" is present for form submission.

Upon form submission, the developer expected the record's ID to be passed to the Delete action in the controller.

However, upon inspection, the controller receives null for the ID. The culprit behind this issue often lies in the form input tag configuration, which we’ll dissect in the following sections.

The Solution Breakdown

1. Reviewing the Input Tag Helper

The original input tag used in the view was:

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

When this code is processed, it generates the following HTML:

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

Key Observation: The generated name attribute is name="Form.Id".

2. The Binding Conundrum

The issue arises because the controller is set up to look for a parameter named id:

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

Since the name of the input from the view does not match what the controller is expecting (id), the model binding process fails and results in the ID being null.

3. Fixing the Issue

To resolve this problem, we need to explicitly set the name attribute of the input tag to match the expected parameter name in the controller:

Here’s the corrected input tag:

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

By explicitly naming the input to match the controller action's parameter, you ensure that the value of Form.Id is properly bound to the id parameter on the server side.

4. Implementation

Here’s how your updated form should look:

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

Conclusion

When building forms in ASP.NET Core MVC, especially for operations like delete actions that require an ID, attention to detail in your input naming conventions is crucial. By ensuring the input name matches the expected parameter in the controller, you can avoid frustrating null values and ensure your application behaves as expected.

If you find yourself stuck with similar issues in the future, return to this solution for guidance, keeping in mind the importance of binding and proper naming conventions in ASP.NET Core MVC.