In ASP.NET Core MVC, how to show the post creator's username in view?

Question

In ASP.NET Core MVC, how to show the post creator's username in view?

asp.net-core-identity asp.net-core-mvc c# entity-framework-core

Question

I'm trying to make a forum web app using ASP.NET Core MVC and Identity. My ForumPost model looks like this:

public class ForumPost
{
    [Key]
    public int PostId { get; set; }

    [Required]
    [MaxLength(32)]
    public string PostName { get; set; }
    [Required]
    public string PostBody { get; set; }
    [Required]
    public IdentityUser User { get; set; }
}

I'm storing the IdentityUser here so in the Posts table, it is replaced by a foreign key to the user Id in the Users table, as explained here. The Create method in my controller looks like this:

public async Task<IActionResult> Create([Bind("PostId,PostName,PostBody")] ForumPost forumPost)
{
    ModelState.Clear();

    var user = await _userManager.GetUserAsync(User);
    forumPost.User = user;

    if (TryValidateModel(forumPost))
    {
        _context.Add(forumPost);
        await _context.SaveChangesAsync();
        return RedirectToAction(nameof(Index));
    }

    return View(forumPost);
}

But when I try to show the creator's Username in the Index.cshtml, it comes up blank. This is the shortened .cshtml:

@model IEnumerable<ForumPost>
@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.PostName)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.User.UserName)
        </td>
    </tr>
}

Am I doing something wrong here? What am I missing? Thanks!

Richard Holmes

View more on Stack Overflow

Richard Holmes · Accepted Answer · 1/28/2020 12:14:18 AM

In the original post, I assumed (and assumed wrong) that the User field in the ForumPost is filled in by automatically grabbing the IdentityUser from the Users table using the foreign key assigned to the ForumPost. It ended up not being the case, and I really don't need the entire user details, just the username.

Therefore, I've changed my ForumPost code to this:

public class ForumPost
{
    [Key]
    public int PostId { get; set; }

    [Required]
    [MaxLength(32)]
    public string PostName { get; set; }

    [Required]
    public string PostBody { get; set; }

    [Required]
    [ForeignKey("User")]
    public string UserId { get; set; }

    public IdentityUser User { get; set; }
}

I've added the UserId there so that the following Index action can have access to it. Doing this won't change the database, since the database already has a User Id foreign key pointing to the Users table. Here is the new Index action:

public async Task<IActionResult> Index()
{
    var posts = await _context.Posts.ToListAsync();
    var postList = new List<PostIndexModel>();
    foreach (var p in  posts)
    {
        var userName = (from u in _context.Users
                    where u.Id.Equals(p.UserId)
                    select u.UserName).SingleOrDefault();
        var post = new PostIndexModel()
        {
            PostId = p.PostId,
            PostName = p.PostName,
            UserName = userName
        };

        postList.Add(post);
    }

    return View(postList);
}

I've also created a new PostIndexModel view model that only shows a few things:

public class PostIndexModel
{
    public int PostId { get; set; }
    [Display(Name = "Post Name")]
    public string PostName { get; set; }
    [Display(Name = "Post Creator")]
    public string UserName { get; set; }
}

In ASP.NET Core MVC, how to show the post creator's username in view?

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