如果 [post] null 显示错误 .Net Core 存储库模式

如何解决如果 [post] null 显示错误 .Net Core 存储库模式

显示 Title == null 的最佳方式是什么？ 我正在使用 .Net Core 并使用存储库模式，当我的文章的 Title 值为 null 时，我无法显示错误表。我需要为这个方法做什么？ 我曾尝试使用这样的代码，但仍然失败，也许我需要使用 Repository？

查看

<div class="row">
<div class="col-lg-9 col-md-12">
    <div class="card card-small mb-3">
        <div class="card-body">
            <form asp-action="SubmitArticle" id="SubmitForm" class="add-new-post">
                <input asp-for="Article.Author" hidden class="form-control" readonly value="@Model.UserFullName"/>
                <partial name="_StatusMessage" model="@ViewData["Message"]"/>
                <input asp-for="Article.Title" class="form-control form-control-lg mb-3" type="text" placeholder="Your Post Title">
                <div class="form-group row">
                    <div class="col-2">
                        <label asp-for="Article.FacultyId" class="col-form-label"></label>
                    </div>
                    <div class="col-5">
                        <select asp-for="@Model.Article.FacultyId" asp-items="@Model.Faculties.Select(f => new SelectListItem() {Text = f.FacultyName.ToString(),Value = f.Id.ToString()})" class="form-control"></select>
                    </div>
                </div>

解决方法

您可以像下面这样更改您的存储库：

public ArticleFacultyViewModel SubmitArticle(ArticleFacultyViewModel articleFacultyViewModel)
    {
        var doesArticleExists = _dbContext.Articles.Include(a => a.Faculty)
                                                    .Where(a => a.Title == articleFacultyViewModel.Article.Title && a.Faculty.Id == articleFacultyViewModel.Article.FacultyId);

            if (articleFacultyViewModel.Article.Title == null)
            {
               return articleFacultyViewModel;
            }
            else
            {
            _dbContext.Articles.Add(articleFacultyViewModel.Article);
            _dbContext.SaveChanges();
            return null;
            }
            
        var model = new ArticleFacultyViewModel()
        {
            Article = articleFacultyViewModel.Article,Faculties = _dbContext.Faculties.ToList(),StatusMessage = "Error: Article already exists in " + _dbContext.Faculties.SingleOrDefault(f => f.Id == articleFacultyViewModel.Article.FacultyId).FacultyName.ToString()
        };

        return model;
    }

然后在你的方法中：

 public IActionResult SubmitArticle(ArticleFacultyViewModel articleFacultyViewModel)
{   
    var articleSubmit = _studentRepository.SubmitArticle(articleFacultyViewModel);
    
     if (articleSubmit == articleFacultyViewModel)
        {
            ModelState.AddModelError("Article.Title","Please Enter Your Title");
        }
        if (ModelState.IsValid)
        {
            if (articleSubmit == null)
            {

                return RedirectToAction(nameof(Index));
            }
         ViewData["Message"] = articleSubmit.StatusMessage;
        }
        return View(articleSubmit);
}

在您看来：

 <input asp-for="Article.Title" class="form-control form-control-lg mb-3" type="text" placeholder="Your Post Title">
 <span asp-validation-for="Article.Title" class="text-danger"></span>