Problem with Blazor InputSelect

Hi @Rusty0918,

Calling context.Entry(Movie).Property(m => m.MovieStarRatingId).IsModified = true; ensures EF Core marks the field as changed, forcing it to be updated.

using var context = DbFactory.CreateDbContext();
context.Entry(Movie).Property(m => m.MovieStarRatingId).IsModified = true;
context.Attach(Movie!).State = EntityState.Modified;

Whole working demo you could follow:

Model

public class Movie
{
    public int Id { get; set; }
    public string? Title { get; set; }
    public DateOnly ReleaseDate { get; set; }
    public string? Genre { get; set; }
    public string? Rating { get; set; }
    [DataType(DataType.Currency)]
    [Column(TypeName = "decimal(18, 2)")]
    public decimal Price { get; set; }
    public MovieStarRating MovieStarRating { get; set; }
    public int MovieStarRatingId { get; set; }
}
public class MovieStarRating
{
    public int Id { get; set; }
    public int Descr { get; set; }
    public List<Movie> Movies { get; set; }
}

Razor Component

@rendermode InteractiveServer
@using Microsoft.EntityFrameworkCore
@using BlazorWebApp9_0.Models
@inject IDbContextFactory<BlazorWebApp9_0.Data.BlazorWebApp9_0Context> DbFactory
@inject NavigationManager NavigationManager
<PageTitle>Edit</PageTitle>
<h1>Edit</h1>
<h2>Movie</h2>
<hr />
@if (Movie is null)
{
    <p><em>Loading...</em></p>
}
else
{
    <div class="row">
        <div class="col-md-4">
            <EditForm method="post" Model="Movie" OnValidSubmit="UpdateMovie" FormName="edit" Enhance>
                <DataAnnotationsValidator />
                <ValidationSummary role="alert" />
                <input type="hidden" name="Movie.Id" value="@Movie.Id" />
                <div class="mb-3">
                    <label for="title" class="form-label">Title:</label>
                    <InputText id="title" @bind-Value="Movie.Title" class="form-control" />
                    <ValidationMessage For="() => Movie.Title" class="text-danger" />
                </div>
                <div class="mb-3">
                    <label for="releasedate" class="form-label">Release Date:</label>
                    <InputDate id="releasedate" @bind-Value="Movie.ReleaseDate" class="form-control" />
                    <ValidationMessage For="() => Movie.ReleaseDate" class="text-danger" />
                </div>
                <div class="mb-3">
                    <label for="genre" class="form-label">Genre:</label>
                    <InputText id="genre" @bind-Value="Movie.Genre" class="form-control" />
                    <ValidationMessage For="() => Movie.Genre" class="text-danger" />
                </div>
                <div class="mb-3">
                    <label for="price" class="form-label">Price:</label>
                    <InputNumber id="price" @bind-Value="Movie.Price" class="form-control" />
                    <ValidationMessage For="() => Movie.Price" class="text-danger" />
                </div>
                <div class="mb-3">
                    <label for="rating" class="form-label">Rating:</label>
                    <InputText id="rating" @bind-Value="Movie.Rating" class="form-control" />
                    <ValidationMessage For="() => Movie.Rating" class="text-danger" />
                </div>
                <div class="mb-3">
                    <label for="moviestarrating" class="form-label:">Movie Star Rating:</label>
                    <InputSelect id="moviestarrating" @bind-Value="Movie.MovieStarRatingId" class="form-control">
                        @foreach (var movieStarRating in StarRatings)
                        {
                            @if (movieStarRating.Id != 0)
                            {
                                <option value="@movieStarRating.Id">@movieStarRating.Descr</option>
                            }
                        }
                    </InputSelect>
                    <ValidationMessage For="() => Movie.MovieStarRating" class="text-danger"></ValidationMessage>
                </div>
                <button type="submit" class="btn btn-primary">Save</button>
            </EditForm>
        </div>
    </div>
}
<div>
    <a href="/movies">Back to List</a>
</div>
@code {
    [SupplyParameterFromQuery]
    private int Id { get; set; }
    [SupplyParameterFromForm]
    private Movie? Movie { get; set; }
    private IList<MovieStarRating> StarRatings { get; set; } = [];
    protected override async Task OnInitializedAsync()
    {
        using var context = DbFactory.CreateDbContext();
        Movie ??= await context.Movie.FirstOrDefaultAsync(m => m.Id == Id);
        if (Movie is null)
        {
            NavigationManager.NavigateTo("notfound");
        }
        StarRatings = await context.MovieStarRating.ToListAsync();       
    }
    private async Task UpdateMovie()
    {
        using var context = DbFactory.CreateDbContext();
        context.Entry(Movie).Property(m => m.MovieStarRatingId).IsModified = true;
        context.Attach(Movie!).State = EntityState.Modified;
        try
        {
            await context.SaveChangesAsync();
        }
        catch (DbUpdateConcurrencyException)
        {
            if (!MovieExists(Movie!.Id))
            {
                NavigationManager.NavigateTo("notfound");
            }
            else
            {
                throw;
            }
        }
        NavigationManager.NavigateTo("/movies");
    }
    private bool MovieExists(int id)
    {
        using var context = DbFactory.CreateDbContext();
        return context.Movie.Any(e => e.Id == id);
    }
}

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Best regards,
Rena

Thank you so much! Yeah it was something simple, as I thought. I'm very new to Blazor and need to learn more the nuances of it!