$select动态属性

本文关键字：属性 动态 select | 更新日期: 2023-09-27 18:02:02

我有以下代码:

public class Book
{
    [Key]
    public string ISBN { get; set; }
    public string Title { get; set; }
    public Press Press { get; set; }
    public IDictionary<string, object> Properties { get; set; }
}
public class BooksController : ODataController
{
    private IList<Book> _books = new List<Book>
    {
        new Book
        {
            ISBN = "978-0-7356-7942-9",
            Title = "Microsoft Azure SQL Database Step by Step",
            Properties = new Dictionary<string, object>
            {
                {"k1","v1"},
                {"k2","v2"}
            }
        },
        new Book
        {
            ISBN = "978-0-7356-8383-9",
            Title = "SignalR",
            Press = new Press
            {
                Name = "Microsoft Press",
                Category = Category.Book
            },
            Properties = new Dictionary<string, object>
            {
                {"k1","v1"}
            }
        }
    };
    [EnableQuery]
    public IQueryable<Book> Get()
    {
        return _books.AsQueryable();
    }
}

当$select用于动态属性时，结果包含许多不包含该属性的空对象。在这个例子中，假设查询是http://localhost:58020/Books?$select=K2，我得到的响应是:

{
  @odata.context: "http://localhost:58020/$metadata#Books(k2)",
  value: [
   {
      k2: "v2"
   },
   { }
  ]
}

如果你观察到它包含一个空花括号来表示一本不包含k2属性的书。如何摆脱这种行为?

$select动态属性

这是《字典》的一期。您可以做的是创建一个名为Parameter的新类，而不是使用Dictionary<String, object>，使用List<Parameter>，如下所示:

class Parameter {
    public String Key;
    public Object Value;
}

修改代码:

public class Book
{
    [Key]
    public string ISBN { get; set; }
    public string Title { get; set; }
    public Press Press { get; set; }
    public List<Parameter> Properties { get; set; }
}
public class BooksController : ODataController
{
    private IList<Book> _books = new List<Book>
    {
        new Book
        {
            ISBN = "978-0-7356-7942-9",
            Title = "Microsoft Azure SQL Database Step by Step",
            Properties = new List<Parameter>
            {
                new Parameter { Key = "k1", Value = "v1" },
                new Parameter { Key = "k2", Value = "v2" }
            }
        },
        new Book
        {
            ISBN = "978-0-7356-8383-9",
            Title = "SignalR",
            Press = new Press
            {
                Name = "Microsoft Press",
                Category = Category.Book
            },
            Properties = new List<Parameter>
            {
                new Parameter { Key = "k1", Value = "v1" }
            }
        }
    };
    [EnableQuery]
    public IQueryable<Book> Get()
    {
        return _books.AsQueryable();
    }
}

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