Скачать или смотреть How to Resolve Model Binding Issues with IList in .Net Core Razor Pages

Learn how to effectively manage multiple `IList` properties using `Model Binding` in .Net Core Razor Pages. This guide covers practical examples and solutions to common issues.
---
This video is based on the question https://stackoverflow.com/q/66851680/ asked by the user 'Henrique Pombo' ( https://stackoverflow.com/u/15242297/ ) and on the answer https://stackoverflow.com/a/66863984/ provided by the user 'Yiyi You' ( https://stackoverflow.com/u/13593736/ ) 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, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: .NetCore - Model Binding with MultipleViews/BindPoperty

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.
---
Understanding Model Binding with Multiple IList Properties in .Net Core

In the world of ASP.NET Core, model binding is a powerful feature that allows you to bind incoming request data to your model properties automatically. However, when dealing with multiple lists using BindProperty, developers sometimes encounter issues, especially when the lists share similar object structures. This guide addresses a common problem where two separate IList properties mistakenly merge into one during model binding and offers a straightforward solution.

The Problem: Merging IList Properties

Let’s consider a practical scenario: you have two lists, SelectedCells and SelectedReferences, each meant to hold a collection of items but retrieve them from different views. Imagine you have 21 Cells, and out of those, 3 are selected, corresponding to 3 References that are to be selected for each cell. Ideally, you would expect:

SelectedCells: 21 objects (corresponding to all cells)

SelectedReferences: 3 objects (for the selected cells only)

However, as per your experience described in the question, both properties (SelectedCells and SelectedReferences) end up containing the same count of objects, causing overlapping data where properties with identical names in your model get overwritten.

Why Does This Happen?

This issue arises because the model binder attempts to map request data to your properties based on the names of the input fields. If the names are not sufficiently differentiated, it may interpret them as the same, leading to incorrect behavior. The question post illustrates that if the views are using the same input field names or if proper binding is not enforced, the two lists can unintentionally merge.

The Solution: Using Name Attributes for Input Fields

To address this issue, you need to explicitly specify different names for the input fields bind to each IList in your views. In this way, they can be correctly distinguished by the model binder. Here’s how to implement this solution:

Step 1: Update the Views

Modify your input fields in both views to include name attributes that are unique to each IList. For example:

For Selected Cells

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

Here, SelectedCells[@ i].Id ensures that each input field for SelectedCells is uniquely identified based on its index in the list.

For Selected References

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

Similarly, this line does the same for the SelectedReferences list.

Step 2: Validation and Testing

After modifying your views, ensure to validate your implementation by testing the functionality with different combinations of selected cells and references. This will help confirm that the model binding works as intended and the data remains distinct and correctly structured in each list.

Final Thoughts

By explicitly differentiating the names attributed to your input fields, you can effectively utilize model binding in ASP.NET Core to handle multiple IList properties without encountering data merging issues. This not only enhances the integrity of your data but also improves the reliability of your application. If you keep a consistent approach and ensure that your naming conventions are clear, the model binding process will work smoothly.

Additional Resources

ASP.NET Core Documentation on Model Binding

Tutorials on Razor Pages for deeper understanding

With these steps, you should now be well-equipped to manage multiple IList properties in ASP.NET Core and ensure that they bind correctly without any unintended merging.