Скачать или смотреть How to Pass Multiple Parameters to a Controller in ASP.NET MVC and ASP.NET Core

Learn how to effectively pass multiple parameters to a controller action in ASP.NET MVC and Core while avoiding common pitfalls.
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This video is based on the question https://stackoverflow.com/q/62677865/ asked by the user 'Colin Aitken' ( https://stackoverflow.com/u/13459877/ ) and on the answer https://stackoverflow.com/a/62768649/ provided by the user 'Karan' ( https://stackoverflow.com/u/9695286/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Pass Multiple Parameters to a Controller in ASP.NET MVC and ASP.NET Core

When developing web applications using ASP.NET MVC or ASP.NET Core, it's common to have controller methods that require multiple parameters. However, developers often face challenges when trying to pass these parameters from a view to the controller. If you've encountered a situation where your method isn't being invoked correctly and instead you receive a 404 error, you're not alone. Let's break down the issue and find a solution.

The Problem Overview

In your approach, you've defined a controller method:

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

And you have a view form intended to submit these parameters:

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Despite this, you find yourself redirected to a 404 error page, indicating that the application is unable to find the specified web address. This typically happens for a few reasons, such as incorrect routing configurations or potential mismatches in parameter names.

Understanding the Cause of the Error

Routing Issues:

When passing parameters to a controller action, the routing configuration needs to be set up correctly. If the routing does not match the expected pattern, your request may not be routed to the controller method.

Parameter Binding:

Ensure the parameter names in the form match those defined in the action method. For instance, if the parameter names differ from those specified in asp-route, the framework won't bind them correctly.

Database Context:

In your method, you are retrieving data from a database and attempting to update it. If you're creating a new object to update an already tracked entity, you might encounter issues when calling _db.SaveChanges().

The Solution

Step 1: Correcting the Routing

To accommodate your method parameters in the routing, you can define a route like this in your startup file:

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

This route allows for optional parameters fromDate and toDate so that they can be routed correctly.

Step 2: Adjusting the Controller Logic

Modify your controller action to ensure it functions as intended. The goal is to prevent any issues related to entity tracking. You have two potential approaches:

Approach 1: Use AsNoTracking()

Use the AsNoTracking() method to prevent the retrieved entities from being tracked by the context. This allows you to create new instances without issues.

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

Approach 2: Modifying Existing Entities

Instead of creating new objects, you can update the already tracked entities directly:

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

Conclusion

By carefully ensuring your routing matches the controller's parameter names and by using correct entity tracking practices, you can successfully pass multiple parameters to your controller in ASP.NET MVC and ASP.NET Core without encountering 404 errors. Implementing these strategies not only resolves the issue but also enhances the maintainability and performance of your application.

With these adjustments, you should avoid further 404 errors and ensure your methods are invoked correctly. Happy coding!