Question

编辑：我正在尝试在我的mvc应用程序中的帖子中添加评论，但我的操作似乎不起作用。当我到达Action时，我希望从Post传递Id（来自表/模型FormalBlog的Id），但newPost.Post = model.Post为null，当动作到达db.SaveChanges时，它会抛出一个System。 Data.Entity.Validation.DbEntityValidationException。

以下是我的操作和我的PostIndexViewModel：

     public ActionResult Comment(PostIndexViewModel model, FormalBlog Post)
    {
        var userName = User.Identity.Name;
        var author = db.Users.SingleOrDefault(x => x.UserName == userName);

        Comment newPost = new Comment();

        newPost.Author = author;
        newPost.Text = model.Text;
        newPost.Post = model.Post;


        db.Comments.Add(newPost);
        db.SaveChanges();
        return RedirectToAction("ShowBlogs", "Blog");

    }
}

public class PostIndexViewModel
{
    public string Id { get; set; }
    public ICollection<FormalBlog> FormalBlogs { get; set; }
    public FormalBlog NewFormalBlog { get; set; } = new FormalBlog();
    public Category NewCategory { get; set; } = new Category();
    public ICollection<Category> Categories { get; set; }
    public List<SelectListItem> SelectedCategories { get; set; }
    public int[] CategoryIds { get; set; }
    public Category CategoryN { get; set; }
    public ICollection<Meeting> Meetings { get; set; } //testrad

   // public int Id { get; set; }
    public string Text { get; set; }
    public ApplicationUser Author { get; set; }
    public Comment NewComment { get; set; }
    public FormalBlog Post { get; set; }

}

以下是我的观点代码：

@model XP_Scrum_Grupp2.Controllers.PostIndexViewModel

@using (Html.BeginForm("Comment", "Blog", new { formal = Model }, FormMethod.Post, new { id = Model.Id }))
{

    <div class="comment-form-container">
        <form class="comment-form" data-action="@Url.Action("Comment", "Blog")">
            @Html.HiddenFor(m => m.Id)

            <div>@Html.DisplayFor(m => m.Author)</div>
            <div>
                <div>@Html.LabelFor(m => m.Text)</div>
                @Html.TextAreaFor(m => m.Text, new { Class = "comment-text", rows = "3", cols = "50" })
            </div>
            <div class="comment-result" style="display: none;">
                <span class="comment-result-text">An error occurred</span>
            </div>
            <div>
                <button type="submit" class="comment-form-submit">Submit comment</button>
            </div>
        </form>
    </div>
}

Answer 1

您没有将任何数据发布为model.NewComment.Text，因此NewComment对象为null时会发生错误。

@Html.TextAreaFor(m => m.Text, new { Class = "comment-text", rows = "3", cols = "50" })

所以，试着改变它;

newPost.Text = model.NewComment.Text;

到

newPost.Text = model.Text;

Answer 2

您的观点未向model.NewComment.Text分配任何值。因此，当您访问model.NewComment时，它将抛出Null引用异常，因为model.Text为空。

您将新文本分配给模型的Test属性。因此，您应该使用model.NewComment.Text代替public ActionResult Comment(PostIndexViewModel model) { var userName = User.Identity.Name; var author = db.Users.SingleOrDefault(x => x.UserName == userName); Comment newPost = new Comment(); newPost.Author = author; newPost.Text = model.Text; newPost.Post = model.Post; db.Comments.Add(newPost); db.SaveChanges(); return RedirectToAction("ShowBlogs", "Blog"); }

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在ASP.NET MVC中添加评论到帖子

2 个答案: