如何使用 Dapper 在 C# 中创建一对多数据结构？

Question

这是我的工作代码：

     string query = @"SELECT DISTINCT
             up.id as unitId,
             af.id as fileId,
             af.reference_id as referenceId,
             af.filename as fileName,
             af.filepath as filePath,
             c.id as categoryId
             u.id as userId
         FROM unit_properties up
         INNER JOIN categories c ON up.category_id = c.id
         INNER JOIN users u ON up.agent_id = u.id
         LEFT JOIN app_files af ON af.reference_id = up.id;";

     var unitProperties = await connection.QueryAsync<UnitProperty, AppFile, Category, User, UnitProperty>(
         query,
         (unit, appFile, category, user) =>
         {
             unit.UnitImages = appFile;
             unit.UnitCategory = category;
             unit.UnitAgent = user;

             return unit;
         },
         splitOn: "referenceId, categoryId, userId"
     );

唯一的问题是，当有多个

unitImages

附加到unit_properties时，该函数返回两个相同的行。

**unitID 1 重复

[
   {
      "unitId":1,
      "unitImages":{
         "fileId":0,
         "referenceId":1,
         "fileName":"exterior1",
         "filePath":"exterior1"
      },
      "unitAgent":{
         "userId":1
      },
      "unitCategory":{
         "categoryId":1
      }
   },
   //another object same as above
]

我需要这样的东西：

"unitId":1,
"unitImages":[
   { 
    "fileId":0,
    "referenceId":1,
    "fileName":"exterior1",
    "filePath":"exterior1"
   },
   { 
    "fileId":1,
    "referenceId":1,
    "fileName":"exterior2",
    "filePath":"exterior2"
   }
],

任何代码建议都将受到高度赞赏。谢谢你。

Answer 1

您可以参考这个一对多示例：
数据库

组.cs

    public class Group
    {
        public int Id { get; set; }
        public string Group_Name { get; set; }
        public ICollection<Student> Students { get; set; }
    }

学生.cs

    public class Student
    {
        public int Student_Id { get; set; }
        public string Student_Name { get; set; }
        public int Group_Id { get; set; }
    }

查询

        [HttpGet]
        public async Task<IActionResult> test()
        {          
            using (var connection = new SqlConnection("Server = 192.168.2.68; Database = test1; User Id = sa; Password = xxxxx;"))
            {
                var groupDictionary = new Dictionary<int, Group>();
                string sql = "SELECT * FROM GroupTable A INNER JOIN StudentTable B ON A.Id = B.Group_Id;";
                var orders = connection.Query<Group, Student, Group>(sql,
                                    (group, student) =>
                                    {
                                        var groupEntry=new Group();
                                        if (!groupDictionary.TryGetValue(group.Id, out groupEntry))
                                        {
                                            groupEntry = group;
                                            groupEntry.Students = new List<Student>();
                                            groupDictionary.Add(groupEntry.Id, groupEntry);                                         
                                        }                                                                            
                                            groupEntry.Students.Add(student);
                                        return groupEntry;
                                    },splitOn:"Student_Id").Distinct(); 
                return Ok(orders);
            }
        }

测试结果