How to Properly Handle MudSelect Change Events in MudBlazor

Описание: Learn the correct way to trigger change events on MudSelect components in MudBlazor for multi-selection in Blazor apps.
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This video is based on the question https://stackoverflow.com/q/79537278/ asked by the user 'user49126' ( https://stackoverflow.com/u/1003222/ ) and on the answer https://stackoverflow.com/a/79538076/ provided by the user 'Qiang Fu' ( https://stackoverflow.com/u/20240963/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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The Problem: MudSelect Change Event Not Firing

When working with MudBlazor's MudSelect component, especially with multi-selection, you may find that the change event does not trigger as expected using typical binding methods.

Here’s an example where the change handler does not fire:

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

The code attempts to use @ bind-SelectedValues:event as an event trigger, which is incorrect.



Understanding @ bind Syntax in Blazor

@ bind-Property creates two-way binding between the property and the component value.

@ bind-Property:event lets you specify the DOM event (like onchange or oninput) that triggers the binding.

However, MudBlazor's MudSelect has a custom pattern for notifying changes, especially on multi-selection.



The Correct Approach: Use @ bind-SelectedValues:after

MudBlazor provides an after event to run code after the binding updates.

Change your markup to:

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

This runs OnLevelChange after _selectedLevels updates, ensuring your handler fires properly.

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



Alternative: One-Way Binding with SelectedValuesChanged

If you prefer manual control:

Bind SelectedValues one-way.

Handle changes with SelectedValuesChanged.

Example:

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

And in code-behind:

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

This pattern gives clearer control over state changes and event handlers.



Summary

Use @ bind-SelectedValues:after to react after two-way bound values update.

Alternatively, handle SelectedValuesChanged event with manual state assignment.

Avoid misusing @ bind-SelectedValues:event as it does not trigger callbacks as expected.

This ensures your MudSelect component fires change events correctly in Blazor apps using MudBlazor.