CODEWITHSUNDEEP
asp.net-core.net-8.0mudblazormudselect
Asisipho Gxumisa
Asisipho Gxumisa

Reputation: 1

Mudselect not working, dropdown empty. What could be the problem here

enter image description here

<MudSelect T="string" Label="Qualification" @bind-Value="selectedQualification">
    @foreach (var qualification in qualifications)
    {
        <MudSelectItem Value="@qualification.Id.ToString()">@qualification.Name</MudSelectItem>
    }
</MudSelect>

The dropdown is empty no data, However when I debug on my

protected override async void OnInitialized()
{
    qualifications = await EducationService.GetQualificationsAsync();

    Console.WriteLine("Qualifications retrieved:");
    foreach (var q in qualifications)
    {
        Console.WriteLine($"ID: {q.Id}, Name: {q.Name}");
    }

    StateHasChanged();
}

qualifications is not empty it comes back with the records. Guid-Id and string-Name

Mudselect, expecting it to return the list of qualifications

Upvotes: 0

Views: 43

Answers (2)

Zhi Lv
Zhi Lv

Reputation: 21636

First, please refer to the Getting started with MudBlazor tutorial to install the MudBlazor package, register the MudServices, and add the relates references and components.

Second, check the relate parameter definition, ensure qualifications has a default value, you can refer to the following sample, it works well on my side.

@page "/select1"
@using MudBlazorServer.Data
@using MudBlazorServer.Services
@inject IEducationService EducationService
<h3>MudSelect1</h3> 
<MudSelect T="string" Label="Qualification" @bind-Value="selectedQualification">
    @foreach (var qualification in qualifications)
    {
        <MudSelectItem Value="@qualification.Name.ToString()">@qualification.Name</MudSelectItem>
    }
</MudSelect>
<div class="d-flex mud-width-full align-center mt-8">
    <MudText Typo="Typo.subtitle1" Class="mr-2">Selected values: </MudText> 
    <MudChip T="string">@(selectedQualification ?? "Select qualifications")</MudChip>
</div>  
@code
{ 
    private List<Qualification> qualifications { get; set; } = new();
    public string selectedQualification { get; set; }
    protected override async void OnInitialized()
    {
        qualifications  = await EducationService.GetQualificationsAsync();  
        Console.WriteLine("Qualifications retrieved:");
        foreach (var q in qualifications)
        {
            Console.WriteLine($"ID: {q.Id}, Name: {q.Name}");
        } 
        //StateHasChanged();
    } 
}

The EducationService:

public interface IEducationService
{
    Task<List<Qualification>> GetQualificationsAsync();
}
public class EducationService : IEducationService
{
    public async Task<List<Qualification>> GetQualificationsAsync()
    { 
       return await Task.Run(() =>
        {
            // Simulating async operation (e.g., fetching from database)
            return new List<Qualification>()
            {
                new Qualification() { Id = Guid.NewGuid(), Name="AAA" },
                new Qualification() { Id = Guid.NewGuid(), Name="BBB" },
                new Qualification() { Id = Guid.NewGuid(), Name="CCC" },
            };
           
        });
    }
}

Register the EducationService service in the Program.cs file

builder.Services.AddScoped<IEducationService, EducationService>();

After running the application, the result as below: The Dropdown works well, and we could get the selected value

result

Upvotes: 1

Emad Kerhily
Emad Kerhily

Reputation: 280

In Blazor, components are rendered before asynchronous operations (like your GetQualificationsAsync call) complete. This means the MudSelect might be rendered before qualifications is populated, resulting in an empty dropdown.

As you say you are sure that your MudSelect is bound successfully. then your problem as I thought is what I mentioned above. To fix it, use OnInitializedAsync instead of OnInitialized. In this way, you allow your process to await the data fetching operation before the component is rendered.

protected override async Task OnInitializedAsync()
{
    qualifications = await EducationService.GetQualificationsAsync();

    Console.WriteLine("Qualifications retrieved:");
    foreach (var q in qualifications)
    {
        Console.WriteLine($"ID: {q.Id}, Name: {q.Name}");
    }

    // No need to call StateHasChanged() explicitly here
}

Upvotes: 0

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