实体框架代码第一个一对多关系使用Web API返回数据

Question

These are my model and I am using entity framework code first approach.

 public class Respondent
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int RespondentId { get; set; }
        public User Requester { get; set; }

        public User Provider { get; set; }
        public string Role { get; set; }

        [NotMapped]
        public ICollection<User> Providers { get; set; }
    }

public class User
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int UserId { get; set; }
        public int UPI { get; set; }
        public string Name { get; set; }


        public string Email { get; set; }


        public bool IsPublic { get; set; }
        [NotMapped]
        public string Profile_Pic { get; set; }
        [NotMapped]
        public string Role { get; set; }
        [NotMapped]
        public List<string> Roles { get; set; }
    }

Now I want to get all respondents by using following web api method but i am not getting correct result set and it is showing null values for Provider and requester and only returning respondent id.

        public IQueryable<Respondent> GetRespondents()
        {
            return db.Respondents;
        }

Answer 1

You can use the Include() function to load related data through your model's navigation properties.

Something like this.

// GET: api/Respondents


public IQueryable<Respondent> GetRespondents() 
{ 
return db.Respondents.
Include(user=>user.Requester)
    .Include(pro=pro.Providers).ToList();
}

Note that if you are using EntityFramework Core, you need the following namespace

using Microsoft.EntityFrameworkCore;

Otherwise you need:

using System.Data.Entity;