Скачать или смотреть Resolving ASP.NET Core MVC Binding Issues with Multi-select Categories

Learn how to fix multi-select category data binding issues in ASP.NET Core MVC, improving data flow between your models and controllers.
---
This video is based on the question https://stackoverflow.com/q/77733063/ asked by the user 'siwm' ( https://stackoverflow.com/u/15905646/ ) and on the answer https://stackoverflow.com/a/77736058/ provided by the user 'siwm' ( https://stackoverflow.com/u/15905646/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, comments, revision history etc. For example, the original title of the Question was: ASP.NET Core MVC Binding Issue

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Troubleshooting Binding Issues in ASP.NET Core MVC: A Guide for Your Blog App

Creating a blog app using ASP.NET Core 8 MVC can be a rewarding learning experience, but it can also lead to some tricky situations. One common problem developers face is related to data binding when handling many-to-many relationships, such as between categories and posts. In this guide, we are going to address a specific issue regarding multi-selection category editing that you might encounter.

Understanding the Problem

In a typical scenario for the PostController, we may want to allow users to edit categories associated with a specific guide. However, when trying to retrieve the selected categories from a multi-select dropdown in the edit form, we might find ourselves with an empty collection. This typically manifests in the following ways:

Missing Category Data: After submitting the form, the categories do not show up in the Post model's Categories property.

Count of Categories: When checking the count of categories in the controller after submission, it returns zero, indicating that the binding did not work.

Let’s examine the solution to this problem.

The Solution

To handle this issue effectively, we need to ensure that the categories are properly bound during the form submission. Here’s how to accomplish that:

Step 1: Modify the Post Model

First, we need to add a property to the Post model, specifically to store the selected category IDs. This will allow us to bind the selected category data:

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

Step 2: Update the Edit Post Endpoint

Next, we need to modify the edit action in the PostController. Here’s how the updated method looks:

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

Step 3: Update the Edit View

Finally, we need to make sure our view correctly binds to the SelectedCategoryIds instead of Categories. Here’s how to update the select dropdown in your Edit Page:

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

Conclusion

By implementing these changes, you should now be able to successfully bind selected categories from a multi-select dropdown in your edit form for the blog app.

Key Points:

Add a SelectedCategoryIds property to the Post model.

Update the Edit method in the PostController.

Bind the view to SelectedCategoryIds in the edit form.

These adjustments ensure that your model accepts the selected categories smoothly, allowing an efficient user experience and solid codebase. Happy coding!