blazor-server-side asp.net-core-8 blazor-component

Blazor (.net core 8) component is never updated

I'm trying to define a component which acts as a bootstrap alert wrapper.

BootstrapAlert.razor

<div class="alert alert-@AlertType d-@(string.IsNullOrEmpty(Message) ? "none" : "block")" role="alert">
    @Message
</div>

@code {
    [ParameterAttribute]
    private string AlertType { get; set; } = "info"; // Default alert type
    [ParameterAttribute]
    private string? Message { get; set; }

    // Method to update the alert type and message
    public async Task ShowAsync(string alertType, string message)
    {
        AlertType = alertType;
        Message = message;
        await InvokeAsync(StateHasChanged);
    }

    // Method to hide the alert
    public async Task HideAsync()
    {
        Message = null;
        await InvokeAsync(StateHasChanged);
    }

     protected override async Task OnParametersSetAsync()
    {
        //Message is ALWAYS null here
        await base.OnParametersSetAsync();
    }

}

Page:

<form class="row" @onsubmit="SubmitForm" @onsubmit:preventDefault>
  <Alert @ref=SaveAlert></Alert>
  <button type="submit">Save</button>        
</form>

@code {
    private Alert? SaveAlert;

private async Task SubmitForm()
{
    try
    {
        await SetIsLoading(true); //DISPLAYS A LOADING SPINNER

        if (SaveAlert != null) await SaveAlert.HideAsync();

        //.......

        if (SaveAlert != null) await SaveAlert.ShowAsync("success", "OK");
    }
    catch (Exception ex)
    {
        if (SaveAlert != null) await SaveAlert.ShowAsync("danger", ex.Message);
    }
    finally
    {
        await SetIsLoading(false);
    }

    StateHasChanged();
}

}

The alert component is never updated, at "OnParametersSetAsync" the "Message" parameter is always null.

I have tryed not async versions of the methods, putting "StateHasChanged" everywhere, not calling the "Hide" method, also removing the [ParameterAttribute] attributes so it were used as a regular variables but nothing seems to work for me

I'm pretty new at blazor so I don't know what else could be relevant. I'm using the app as RenderMode="Server"

What I'm doing wrong?

Solution

First: ensure you have the render mode set globally:

App.razor

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <base href="/" />
    <link rel="stylesheet" href="bootstrap/bootstrap.min.css" />
    <link rel="stylesheet" href="app.css" />
    <link rel="stylesheet" href="SO79011986.styles.css" />
    <link rel="icon" type="image/png" href="favicon.png" />
    <HeadOutlet @rendermode="InteractiveServer" />
</head>

<body>
    <Routes @rendermode="InteractiveServer" />
    <script src="_framework/blazor.web.js"></script>
</body>

</html>

At the moment your code won't compile properly, so I'm not sure how you're debugging the presented code. You're declaring the Parameters as private when they should be public.

At a more general level, you've overcomplicating the code because you're new to Blazor and still acquiring the necessary knowledge.

Here's a more succinct way to build an alert using binding. Capturing instances with @ref is OK, but such tight coupling between components is best avoided if possible.

A data object to hold the alert state.

public readonly record struct AlertData(bool Show, string AlertType, string Message);

Alert.razor

<div hidden="@_hidden" class="@_css" role="alert">
    @this.Value.Message
</div>

@code {
    // These are the bind parameters
    [Parameter] public AlertData Value { get; set; }
    [Parameter] public EventCallback<AlertData> ValueChanged { get; set; }

    private string _css => $"alert alert-{this.Value.AlertType}";
    private bool _hidden => !this.Value.Show;

    // If you had a dismiss button
    private void Dismiss()
    {
        this.ValueChanged.InvokeAsync(new AlertData(false, string.Empty, string.Empty));
    }
}

Demo:

@page "/"

<PageTitle>Home</PageTitle>

<h1>Hello, world!</h1>

Welcome to your new app.

<Alert @bind-Value="_alertData" />

<div class="m-2">
    <button class="btn btn-primary" @onclick="this.SubmitForm">Save</button>
</div>
@code {
    private AlertData _alertData = new(false, string.Empty, string.Empty);
    private bool _toggleState;

    private async Task SubmitForm()
    {
        _alertData = new(false, string.Empty, string.Empty);

        // UI Event Handler will render the component here and create a render cascade on sub-components with changed parameters
        await SetIsLoading(true);

        if (_toggleState)
            _alertData = new(true, "success", "Ok");
        else
            _alertData = new(true, "danger", "Failed");

        _toggleState = !_toggleState;

        await SetIsLoading(false);
        // UI Event Handler will render the component here and create a render cascade on sub-components with changed parameters
    }

    private async ValueTask SetIsLoading(bool show)
    {
        // Do whatever
        await Task.Yield();
    }
}