Question

我有以下课程：

public class Blog {
    public int Id {get; set;}
    public String Name {get; set;}
    ...
    ...
    public int CatId {get;set;}
}

public class BlogCategory{
    public int Id {get; set;}
    public String Name {get; set;}
    public virtual Blogs {get; set;}
}

现在我的剃须刀页面上有视图模型：

public BlogViewModel{
    public int Id {get; set;}
    public string Name {get; set;}
    ..
    ..
    public string CategoryName {get; set;}
}

我正在尝试选择博客并包含其类别名称：我的查询：

Blogs = await _context.Blogs
    .Select(b => new BlogViewModel()
    {
        Id = b.Id,
        Name = b.Name,        
        //CategoryName = 
    })
    .ToListAsync();

如何根据我拥有的CatId从BlogCategory表中选择类别名称？

一种方法是添加

public virtual Category BlogCat {get; set;}

到Blog类，然后使用Include，但我不想使用此方法，因为我只希望Category Name（名称）而不是完整对象。

有什么帮助吗？

解决方案：

Blogs = await _context.Blogs
        .Select(b => new BlogViewModel()
        {
            Id = b.Id,
            Name = b.Name,        
            CategoryName = _context.BlogCategory
                        .Where(c => c.Id == b.CatId)
                        .Select(c => c.Name)
                        .SingleOrDefault()
        })
        .ToListAsync();

Answer 1

    var blogModels = ( from b in _context.Blogs 
     join c in _context.BlogCategories 
     on b.CatId equals c.Id
     select new BlogViewModel()
      {
       Id = b.Id,
       Name = b.Name,        
       CategoryName = c.Name
        }).ToList();

Answer 2

解决方案：

Blogs = await _context.Blogs
        .Select(b => new BlogViewModel()
        {
            Id = b.Id,
            Name = b.Name,        
            CategoryName = _context.BlogCategory
                        .Where(c => c.Id == b.CatId)
                        .Select(c => c.Name)
                        .SingleOrDefault()
        })
        .ToListAsync();

使用实体框架基于ID从另一个表中选择列

2 个答案: