然后在Create和Edit的Action中去绑定对应的下拉菜单即可。

注意：List 集合的CategorySelectItemListView，这个是新建的ViewModel对象，用来专门绑定下拉菜单使用，其代码如下：

public class CategorySelectItemListView
{
public int Id { get; set; }
public string Title { get; set; }
public int ParentId { get; set; }
public List Children { get; set; }
public CategorySelectItemListView()
{
Children = new List();
}

public CategorySelectItemListView(int id,string title,int parentid)
{
this.Id = id;
this.Title = title;
this.ParentId = parentid;
Children = new List();
}

public CategorySelectItemListView(int id, string title, CategorySelectItemListView parent)
{
this.Id = id;
this.Title = title;
this.ParentId = parent.Id;
Children = new List();
}

（3）.视图Edit代码，注解部分的代码可以参考，我尝试用过，也可以达到目的，演练代码最好是用多种方式实现，查看其区别，这样掌握的牢固一些。

@{ ViewData["Title"] = "编辑文章"; }
@model Article
@section Scripts{

}

（4）.视图Index列表的代码

针对列表的显示，又专门编写了ArticeView的这个ViewModel。

public class ArticleView
{
public int Id { get; set; }
public int CategoryId { get; set; }
public string CategoryName { get; set; }
public string Title { get; set; }
public int ViewCount { get; set; }
public int Sort { get; set; }
public string Author { get; set; }
public string Source { get; set; }
public int AddManagerId { get; set; }
public DateTime AddTime { get; set; }
}

@using Humanizer;
@using RjWebCms.Db;
@using RjWebCms.Models.Articles;
@model PaginatedList
@{
ViewData["Title"] = "文章列表";
}
@section Scripts{

}

（5）.Controller部分的全部代码，注意看代码注释

public class ArticleController : Controller
{
private readonly IHostEnvironment _hostEnvironment;
private readonly IArticleService _articleService;
private readonly IArticleCategoryService _articleCategoryService;
private readonly AppDbContext _appDbContext;
public ArticleController(IArticleService articleService, IArticleCategoryService articleCategoryService,AppDbContext appDbContext,IHostEnvironment hostEnvironment)
{
_hostEnvironment = hostEnvironment;
_appDbContext = appDbContext;
_articleService = articleService;
_articleCategoryService = articleCategoryService;
}

    public async Task<IActionResult> Index(string sortOrder, string currentFilter, string searchString, int? pageNumber)  
    {  
        ViewData\["CurrentSort"\] = sortOrder;  
        ViewData\["NameSortParm"\] = String.IsNullOrEmpty(sortOrder) ? "name\_desc" : "";  
        ViewData\["DateSortParm"\] = sortOrder == "Date" ? "date\_desc" : "Date";

        if (searchString != null)  
        {  
            pageNumber = 1;  
        }  
        else  
        {  
            searchString = currentFilter;  
        }  
        ViewData\["CurrentFilter"\] = searchString;  
        var article = from s in \_appDbContext.Article  
                      join p in \_appDbContext.ArticleCategory on s.CategoryId equals p.Id  
                      select new ArticleView {  
                        Id = s.Id,  
                        CategoryId = s.CategoryId,  
                        CategoryName = p.Title,  
                        Title = s.Title,  
                        Sort = s.Sort,  
                        AddManagerId = s.AddManagerId,  
                        AddTime = s.AddTime,  
                        Author = s.Author,  
                        Source = s.Source,  
                        ViewCount = s.ViewCount,  
                      };  
        if (!string.IsNullOrEmpty(searchString))  
        {  
            article = article.Where(s => s.Title.Contains(searchString));  
        }  
        switch (sortOrder)  
        {  
            case "name\_desc":  
                article = article.OrderByDescending(s => s.Title) ;  
                break;  
            case "Date":  
                article = article.OrderBy(s => s.AddTime);  
                break;  
            case "date\_desc":  
                article = article.OrderByDescending(s => s.AddTime);  
                break;  
            default:  
                article = article.OrderBy(s => s.Title);  
                break;  
        }  
        int pageSize = 4;  
        return View(await PaginatedList<ArticleView>.CreateAsync(article.AsNoTracking(), pageNumber ?? 1, pageSize));  
    }

    \[HttpGet\]  
    public async Task<IActionResult> CreateAsync()  
    {  
        #region 绑定类别下拉框  
        var categories = await \_articleCategoryService.GetArticleCategory();//列出文章类别字典  
        var categoryItems = new List<SelectListItem>()  
        {  
            new SelectListItem(){ Value="0",Text="全部",Selected=true}  
        };  
        //全部列出并转成DropDownList对象  
        List<CategorySelectItemListView> list = new List<CategorySelectItemListView>();  
        foreach (var category in categories)  
        {  
            list.Add(new CategorySelectItemListView {  
                Id=category.Id,  
                Title = category.Title,  
                ParentId = category.ParentId  
            });  
        }

        #region 循环嵌套调用  
        //List<CategorySelectItemListView> list1 = GetChildCategory(list);  
        //foreach (var li in list1)  
        //{  
        //    categoryItems.Add(new SelectListItem { Value = li.Id.ToString(), Text = li.Title });  
        //    if (li.Children.Count > 0)  
        //    {  
        //        foreach(var t in li.Children)  
        //            categoryItems.Add(new SelectListItem { Value = t.Id.ToString(),Text= "|-" + t.Title });  
        //    }  
        //}  
        #endregion

        #region  递归调用  
        List<CategorySelectItemListView> list1 = GetChildCategory(list, new List<CategorySelectItemListView>(), 0);  
        foreach (var li in list1)  
        {  
            categoryItems.Add(new SelectListItem { Value = li.Id.ToString(), Text = li.Title });  
            if (li.Children.Count > 0)  
            {  
                foreach (var t in li.Children)  
                    categoryItems.Add(new SelectListItem { Value = t.Id.ToString(), Text = "  |-" + t.Title });  
            }  
        }  
        #endregion

        ViewBag.database = categoryItems;  
        #endregion  
        return View();  
    }

    \[HttpPost\]  
    \[ValidateAntiForgeryToken\]  
    public async Task<IActionResult> CreateAsync(Article article,\[FromForm\]IFormCollection fromData)  
    {  
        //去掉对字段IsSystem的验证,IsSystem在数据库是bool类型,而前端是0和1，ModelState的验证总是报false，所以去掉对其验证  
        //ModelState.Remove("IsSystem");//在View端已经解决了了bool类型，那么此行代码可以不用  
        #region 下拉菜单  
        string strCategoryId = Request.Form\["ddl\_CategoryId"\];  
        if (!string.IsNullOrEmpty(strCategoryId))  
            article.CategoryId = int.Parse(strCategoryId);  
        else  
            article.CategoryId = 0;  
        #endregion

        #region 复选框  
        article.IsTop = fromData\["IsTop"\] != "false";//使用FormCollection时，可以这样  
        article.IsRed = fromData\["IsRed"\] != "false";  
        article.IsSlide = fromData\["IsSlide"\] != "false";  
        //也可以这样取值，但要注意View内的写法  
        //if (!string.IsNullOrEmpty(fromData\["IsTop"\]))  
        //    article.IsTop = true;  
        //else  
        //    article.IsTop = false;  
        #endregion

        #region 上传文件  
        IFormFileCollection files = fromData.Files;  
       foreach(var formFile in files)  
        {  
            //var fileName = ContentDispositionHeaderValue.Parse(file.ContentDisposition).FileName.Trim('"');  
            string webContentPath = \_hostEnvironment.ContentRootPath;  
            var fileExt = formFile.FileName.Substring(formFile.FileName.LastIndexOf('.'));//文件扩展名  
            var fileNew = DateTime.Now.ToString("yyyyMMddHHmmss") + fileExt; //给文件重新命名

            //string upLoadPath = webContentPath + $@"\\{fileName}";  
            string upLoadPath = webContentPath + $@"\\UpFiles";  
            var fileUrl = upLoadPath + $@"\\{fileNew}";

            if (formFile.Length > 0)  
            {  
                using (var stream = new FileStream(fileUrl,FileMode.Create))  
                {  
                    await formFile.CopyToAsync(stream);  
                }  
            }  
            article.ImageUrl = "../UpFiles/" + fileNew;

        }  
        #endregion 

        if (ModelState.IsValid)  
        {  
            var successful = await \_articleService.AddArticleAysnc(article);  
            if (successful)  
                return RedirectToAction("Index");  
            else  
                return BadRequest("失败");  
        }  
        return View(article);  
    }

    \[HttpGet\]  
    public async Task<IActionResult> Edit(int id)  
    {

        if (string.IsNullOrEmpty(id.ToString()))  
            return NotFound();

        var article = await \_articleService.FindArticleAsync(id);  
        if (article == null)  
            return NotFound();

        #region 绑定角色下拉框  
        var categories = await \_articleCategoryService.GetArticleCategory();//列出文章类别字典  
        var categoryItems = new List<SelectListItem>()  
        {  
            new SelectListItem(){ Value="0",Text="全部",Selected=true}  
        };  
        //全部列出并转成DropDownList对象  
        List<CategorySelectItemListView> list = new List<CategorySelectItemListView>();  
        foreach (var category in categories)  
        {  
            list.Add(new CategorySelectItemListView  
            {  
                Id = category.Id,  
                Title = category.Title,  
                ParentId = category.ParentId  
            });  
        }  
        #region  递归调用  
        List<CategorySelectItemListView> list1 = GetChildCategory(list, new List<CategorySelectItemListView>(), 0);  
        foreach (var li in list1)  
        {  
            categoryItems.Add(new SelectListItem { Value = li.Id.ToString(), Text = li.Title });  
            if (li.Children.Count > 0)  
            {  
                foreach (var t in li.Children)  
                    categoryItems.Add(new SelectListItem { Value = t.Id.ToString(), Text = "  |-" + t.Title });  
            }  
        }  
        #endregion

        #region 遍历并选中  
        foreach (SelectListItem item in categoryItems)  
        {  
            if (item.Value == article.CategoryId.ToString())  
                item.Selected = true;  
        }  
        #endregion  
        ViewBag.database = categoryItems;  
        #endregion

        return View(article);  
    }

    \[HttpPost\]  
    \[ValidateAntiForgeryToken\]  
    public async Task<IActionResult> Edit(int id, \[FromForm\]Article article)  
    {  
        if (id != article.Id)  
        {  
            return NotFound();  
        }  
        #region 下拉菜单  
        string strCategoryId = Request.Form\["ddl\_CategoryId"\];  
        if (!string.IsNullOrEmpty(strCategoryId))  
            article.CategoryId = int.Parse(strCategoryId);  
        else  
            article.CategoryId = 0;  
        #endregion  
        #region 复选框  
        if (Request.Form\["IsTop"\].Contains("true"))  
            article.IsTop = true;  
        else  
            article.IsTop = false;  
        if (Request.Form\["IsRed"\].Contains("true"))  
            article.IsRed = true;  
        else  
            article.IsRed = false;  
        if (Request.Form\["IsSlide"\].Contains("true"))  
            article.IsSlide = true;  
        else  
            article.IsSlide = false;  
        #endregion  
        //ModelState.Remove("IsTop");  
        //ModelState.Remove("IsRed");  
        //ModelState.Remove("IsSlide");  
        if (ModelState.IsValid)  
        {  
            try  
            {  
                var result = await \_articleService.UpdateArticleAsync(id, article);  
                //跳转  
                if (result)  
                    return RedirectToAction("Index");  
                else  
                    return BadRequest("编辑失败");  
            }  
            catch (Exception ex)  
            {  
                return BadRequest("编辑失败");  
            }  
        }  
        else  
        {  
            return BadRequest("数据输入有误！");  
        }  
    }

    /// <summary>  
    /// 递归函数，实现获取子菜单  
    /// </summary>  
    /// <param name="lists">递归前的列表</param>  
    /// <param name="newlists">递归后的新列表</param>  
    /// <param name="parentId">父Id</param>  
    /// <returns></returns>  
    public static List<CategorySelectItemListView> GetChildCategory(List<CategorySelectItemListView> lists, List<CategorySelectItemListView> newlists, int parentId)  
    {  
        newlists = new List<CategorySelectItemListView>();  
        List<CategorySelectItemListView> tempList = lists.Where(c => c.ParentId == parentId).ToList();  
        for (int i = 0; i < tempList.Count; i++)  
        {  
            CategorySelectItemListView category = new CategorySelectItemListView();  
            category.Id = tempList\[i\].Id;  
            category.ParentId = tempList\[i\].ParentId;  
            category.Title = tempList\[i\].Title;  
            category.Children = GetChildCategory(lists, newlists, category.Id);  
            newlists.Add(category);  
        }  
        return newlists;  
    }

    /// <summary>  
    /// 循环嵌套，实现获取子菜单  
    /// </summary>  
    /// <param name="lists">循环遍历前的列表</param>  
    /// <returns></returns>  
    public static List<CategorySelectItemListView> GetChildCategory(List<CategorySelectItemListView> lists)  
    {  
        List<CategorySelectItemListView> categorylist = new List<CategorySelectItemListView>();  
        for (int i = 0; i < lists.Count; i++)  
        {  
            if (0 == lists\[i\].ParentId)  
                categorylist.Add(lists\[i\]);

            for (int j = 0; j < lists.Count; j++)  
            {  
                if (lists\[j\].ParentId == lists\[i\].Id)  
                    lists\[i\].Children.Add(lists\[j\]);  
            }  
        }  
        return categorylist;  
    }

}

（6）.Service应用层代码

public class ArticleService : IArticleService  
{  
    private readonly AppDbContext \_appDbContext;  
    public ArticleService(AppDbContext appDbContext)  
    {  
        \_appDbContext = appDbContext;  
    }  
    /// <summary>  
    /// 添加文章  
    /// </summary>  
    /// <param name="article"></param>  
    /// <returns></returns>  
    public async Task<bool> AddArticleAysnc(Article article)  
    {  
        article.IsDeleted = false;  
        article.AddManagerId = 1;//用户id  
        article.AddTime = DateTime.Now;  
        article.IsPublish = true;  
        await \_appDbContext.Article.AddAsync(article);  
        var result = await \_appDbContext.SaveChangesAsync();  
        return result == 1;  
    }

    /// <summary>  
    /// 删除文章  
    /// </summary>  
    /// <param name="Id"></param>  
    /// <returns></returns>  
    public async Task<bool> DeleteArticleAsync(int Id)  
    {  
        var article = await \_appDbContext.Article.FirstOrDefaultAsync(x => x.Id == Id);  
        if (article != null)  
        {  
            \_appDbContext.Article.Remove(article);  
        }  
        var result = await \_appDbContext.SaveChangesAsync();  
        return result == 1; //注意(result==1 如果等式成立，则返回true，说明删除成功)  
    }

    /// <summary>  
    /// 按Id查询文章  
    /// </summary>  
    /// <param name="Id"></param>  
    /// <returns></returns>  
    public async Task<Article> FindArticleAsync(int Id)  
    {  
        var item = await \_appDbContext.Article.Where(x => x.Id == Id).FirstOrDefaultAsync();  
        return item;  
    }

    /// <summary>  
    /// 按标题查询文章  
    /// </summary>  
    /// <param name="title"></param>  
    /// <returns></returns>  
    public async Task<Article\[\]> GetArtcleByTitle(string title)  
    {  
        var items = await \_appDbContext.Article.Where(x => x.Title.Contains(title)).ToArrayAsync();  
        return items;  
    }

    /// <summary>  
    /// 查询文章  
    /// </summary>  
    /// <returns></returns>  
    public async Task<Article\[\]> GetArticles()  
    {  
        var items = await \_appDbContext.Article.Where(x => x.IsDeleted==false).ToArrayAsync();  
        return items;  
    }

    /// <summary>  
    /// 更新文章  
    /// </summary>  
    /// <param name="id"></param>  
    /// <param name="article"></param>  
    /// <returns></returns>  
    public async Task<bool> UpdateArticleAsync(int id, Article article)  
    {  
        var oldArticle = await  FindArticleAsync(id); //找出旧对象

        //将新值赋到旧对象上  
        oldArticle.Title = article.Title;  
        oldArticle.CategoryId = article.CategoryId;  
        oldArticle.SeoDescription = article.SeoDescription;  
        oldArticle.SeoTitle = article.SeoTitle;  
        oldArticle.SeoKeyword = article.SeoKeyword;  
        oldArticle.Content = article.Content;  
        oldArticle.Sort = article.Sort;  
        oldArticle.Source = article.Source;  
        oldArticle.IsSlide = article.IsSlide;  
        oldArticle.IsPublish = article.IsPublish;  
        oldArticle.IsRed = article.IsRed;  
        oldArticle.IsTop = article.IsTop;  
        oldArticle.ViewCount = article.ViewCount;  
        oldArticle.Author = article.Author;  
        oldArticle.ImageUrl = article.ImageUrl;

        oldArticle.ModifyManagerId = 11;//  
        oldArticle.ModifyTime = DateTime.Parse(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));

        //对旧对象执行更新  
        \_appDbContext.Entry(oldArticle).State = EntityState.Modified;  
        var result = await \_appDbContext.SaveChangesAsync();  
        return result == 1;  
    }  
}

再谈CheckBox的使用

1.在View视图页增加的代码格式如果为：

置顶

或者是这样：

置顶

那么在生成的html代码中，都会自动成id，name，type=“checkbox” value的属性。

2.在Controller中进行取值时的代码为：

if (Request.Form["IsTop"].Contains("true"))

article.IsTop = true;

else

article.IsTop = false;

跟踪时发现，View中Checkbox选中是，会产生true和false两个值，如图跟踪变量发现:

如此，取值时，就用了Contains功能，因为View中CheckBox没选中，这只有一个false值；

3.在View视图页增加代码的格式如果为：

置顶

4.在Controller中进行取值时的代码为：

if (!string.IsNullOrEmpty(Request.Form["IsTop"]))

article.IsTop = true;

else

article.IsTop = false;

跟踪时发现，View中的CheckBox选中是，取到的值为“on”，如图跟踪发现：

所以，才用了IsNullOrEmpty这个函数，依据判空来确定是否选中。

但是这样写有个问题，在ModelState.IsValid()的模型验证中，一直无法通过，IsTop一直为false，为此，我干脆就把其去除掉验证：

ModelState.Remove("IsTop");//去除name=IsTop的checkbox的模型验证

5.使用Checkbox，还是要看给在数据表中为其定义的字段类型，Model中的指定类型和验证属性，如果你赋予了Value值，那么就在Controller中取值，Asp.Net Core中Checkbox默认是True和False的值，网上关于@Html.CheckBox()形式也行，你可以尝试跟踪变量值来判断如何处理，其宗旨就是根据具体条件来处理。