在 ASP.NET MVC 中向 post 添加注释

Question

编辑：我试图在我的 mvc 应用程序中向 post 添加评论，但我的操作似乎不起作用。当我到达 Action 时，我想传递来自 Post 的 Id（来自 table/model FormalBlog 的 Id）但是 newPost.Post = model.Post 为 null 并且当操作到达 db.SaveChanges 它抛出一个 System.Data.Entity.Validation.DbEntityValidationException。

下面是我的操作和我的 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; }

}

这是我的观点的代码：

@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

您没有将任何数据作为 model.NewComment.Text 发布，因此发生错误是因为 NewComment 对象是 null。

@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;

至

newPost.Text = model.Text;

Answer 2

您的观点没有为 model.NewComment 赋予任何价值。因此，当您访问 model.NewComment.Text 时，它将抛出 Null 引用异常，因为 model.NewComment 为空。

您将新文本分配给模型的测试属性。所以你应该使用 model.Text 而不是 model.NewComment.Text

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");

    }

在 ASP.NET MVC 中向 post 添加注释

Adding comment to post in ASP.NET MVC

c#

asp.net

action

asp.net-mvc-5