使用C＃

Question

我需要一些关于如何使用Dapper将数据导入多个列表对象，然后将列表序列化为适当的JSON格式的建议。请分享您的建议。谢谢！

1。样本JSON格式

{
  "students": [
    {
      "studentId": "",
      "emailAddresses": [
        {
          "emailAddress": ""
        }
      ],      
      "lastName": "",
      "directory": {
        "addresses": [
          {
            "city": "",
            "state": ""
          }
        ],      
      }     
    }
  ]
}

2。类

public class Student
{
    public string StudentId { get; set; }
    public string Gender { get; set; }  
    public List<EmailAddresses> emailAddresses { get; set; }
}

public class EmailAddresses
{
    public string EmailAddress { get; set; }    
}

第3。来自sql查询的数据

StudentId   Gender  EmailAddress
123456  Female  maryjoe@gmail.com
123456  Female  mary.joe@mycollege.edu
123456  Female  mj@hotmail.com

4。我正在尝试实施的Dapper代码

 public List<Student> GetStudentData()
 {
     List<Student> dataStudent;
     using (IDbConnection connection = RepositoryHelper.OpenConnection())
     {
         dataStudent = connection.Query<Student, EmailAddresses, Student>("mystoredprocedure",
            (c, cc) =>
            {
                c.EmailAddresses = cc;
                return c;
            }, splitOn: "EmailAddress").ToList();

        }

    return dataStudent;
}

4。序列化为JSON

static void Main(string[] args)
{            
    List<Student> students = GetStudentData();
    var json = new System.Web.Script.Serialization.JavaScriptSerializer()
                                                  .Serialize(students);
}

Answer 1

第一个问题是您在调用存储过程时未指定命令类型是存储过程。这会将您的proc名称错误地转换为sql命令，这显然会失败。

但是，根据您更新的评论，第二个问题是您误用了dapper的多映射器功能。此功能用于将多个表映射到多个对象。但是，您的存储过程似乎为您提供了一个展平对象，您需要根据学生ID拆分唯一记录，将电子邮件地址映射到您的电子邮件地址属性。

动态效果非常好，因为我们可以即时映射数据。

public List<Student> GetStudentData()
{
    List<Student> dataStudent;
    using (IDbConnection connection = RepositoryHelper.OpenConnection())
    {
        dataStudent = connection.Query<dynamic>(
            "mystoredprocedure", 
            commandType: CommandType.StoredProcedure)
                .GroupBy(x => x.StudentId)
                .Select(x => new Student 
                    { 
                        StudentId = x.First().StudentId, 
                        Gender = x.First().Gender,
                        emailAddresses = x.Select(ea => new EmailAddresses 
                            { 
                                EmailAddress = ea.emailAddresses 
                            }).ToList()
                    }).ToList();

        return dataStudent;
    }
}