使用带有 DTO 的 lambda/linq c# 进行多表连接

Question

这真的把我难住了。我在数据库中有四个表，不幸的是设计这个表的人没有创建引用约束。因此，没有可用的导航属性。

四个表是：

CiscoPhoneReport
ApplicationSummary
CSQActivityReport
CallDistributionSummary

这个想法是，对于 CiscoPhoneReport 中的每个PhoneReportID，有一个ApplicationSummary、三个CSQActivityReport 和三个CallDistributionSummary。

我想要以下 JSON 格式的输出：

`[{
   "appSummary":{
   "startDate":"2015-09-01T00:00:00",
   "endDate":"2015-09-30T00:00:00",
   "applicationName":"RationalDrugTherapy",
   "callsPresented":14504,
   "callsAbandoned":1992,
   "callsHandled":12512
  },
  "csqModel":[
   {
     "startDate":null,
     "csqid":"3",
     "callsPresented":6271,
     "avgQueueTime":"00:00:21",
     "callsHandled":0,
     "avgAnswerSpeed":"00:00:00",
     "avgHandleTime":"00:02:08",
     "callsHandledGreaterThan3t":5742,
     "callsAbandoned":99,
     "avgAbandonTime":"00:02:20",
     "maxQueueTime":"00:25:26",
     "maxHandleTime":"00:19:33",
     "maxAbandonTime":"00:17:50"
   },{
     "startDate":null,
     "csqid":"3",
     "callsPresented":6271,
     "avgQueueTime":"00:00:21",
     "callsHandled":0,
     "avgAnswerSpeed":"00:00:00",
     "avgHandleTime":"00:02:08",
     "callsHandledGreaterThan3t":1728,
     "callsAbandoned":99,
     "avgAbandonTime":"00:02:20",
     "maxQueueTime":"00:25:26",
     "maxHandleTime":"00:19:33",
     "maxAbandonTime":"00:17:50"
  }, {
    "startDate":null,
    "csqid":"3",
    "callsPresented":6271,
    "avgQueueTime":"00:00:21",
    "callsHandled":0,
    "avgAnswerSpeed":"00:00:00",
    "avgHandleTime":"00:02:08",
    "callsHandledGreaterThan3t":3363,
    "callsAbandoned":99,
    "avgAbandonTime":"00:02:20",
    "maxQueueTime":"00:25:26",
    "maxHandleTime":"00:19:33",
    "maxAbandonTime":"00:17:50"
  }]
}]`

为此，我创建了 DTO：

`public class AppSummary
 {
   public string PhoneReportID { get; set; }
   public DateTime StartDate { get; set; }
   public DateTime EndDate { get; set; }
   public string ApplicationName { get; set; }
   public int CallsPresented { get; set; }
   public int CallsAbandoned { get; set; }
   public int CallsHandled { get; set; }
 }
`

`public class CSQModel
    {
        public string StartDate { get; set; }
        public string CSQID { get; set; }
        public int CallsPresented { get; set; }
        public TimeSpan AvgQueueTime { get; set; }
        public int CallsHandled { get; set; }
        public TimeSpan AvgAnswerSpeed { get; set; }
        public TimeSpan AvgHandleTime { get; set; }
        public int CallsHandledGreaterThan3t { get; set; }
        public int CallsAbandoned { get; set; }
        public TimeSpan AvgAbandonTime { get; set; }
        public TimeSpan MaxQueueTime { get; set; }
        public TimeSpan MaxHandleTime { get; set; }
        public TimeSpan MaxAbandonTime { get; set; }      
    }
`

`public class PhoneReport
    {
        public AppSummary AppSummary { get; set; }
        //Initially, I had it like this
        public CSQModel CSQModel { get; set; }

        //I renamed the property as LIST to see if I could use it and add data to the list in linq, but I couldn't use the list within select expression in linq.
        //public List<CSQModel> CSQModel { get; set; }

    }
`

CSQModel 类需要来自CSQActivityReport 和CallDistributionSummary 表的数据。

我能够创建一个带有表连接的 linq 语句，如下所示。

var res = from cpr in db.CiscoPhoneReport 
        join app in db.ApplicationSummary on cpr.PhoneReportID equals          app.PhoneReportID into g1
        from appGroup in g1.DefaultIfEmpty()
        join csq in db.CSQActivityReport on cpr.PhoneReportID equals csq.PhoneReportID into g2
        from csqGroup in g2.DefaultIfEmpty()
        join call in db.CallDistributionSummary on cpr.PhoneReportID equals call.PhoneReportID into g3
        from callGroup in g3.DefaultIfEmpty()
        where cpr.PhoneReportID == phoneReportID
        select new PhoneReport
        {
           AppSummary = new AppSummary
          {
             StartDate = cpr.StartDate,
             EndDate = cpr.EndDate,
             ApplicationName = appGroup.ApplicationName,
             CallsPresented = appGroup.CallsPresented,
             CallsAbandoned = appGroup.CallsAbandoned,
             CallsHandled = appGroup.CallsHandled

         },
         CSQModel = new CSQModel
         {
             CSQID = csqGroup.CSQID.ToString(),
             CallsPresented = csqGroup.CallsPresented,
             AvgQueueTime = csqGroup.AvgQueueTime,                                                
             AvgHandleTime = csqGroup.AvgHandleTime, 
             CallsHandledGreaterThan3t = callGroup.CallsHandledGreaterThan3t, 
             CallsAbandoned = csqGroup.CallsAbandoned,
             AvgAbandonTime = csqGroup.AvgAbandonTime,
             MaxQueueTime = csqGroup.MaxQueueTime,
             MaxHandleTime = csqGroup.MaxHandleTime,
             MaxAbandonTime = csqGroup.MaxAbandonTime
         }
   };
`

我得到的结果是一组有 9 行的数据，这是有道理的——就像 SQL 中的内连接一样。但这不是我想要的。

如何获取上述 JSON 格式的数据？我根本想不通。

Answer 1

我认为您看到 9 条记录的部分原因是您使用的语法是 left outer joins in Linq 的语法。

可能有用的是使用子查询以您想要的格式获取您想要的数据。

例如

var res = from cpr in db.CiscoPhoneReport
          join app in db.ApplicationSummary on cpr.PhoneReportID equals app.PhoneReportID
          where cpr.PhoneReportID == phoneReportID
          select new PhoneReport
          {
              AppSummary = new AppSummary
              {
                  // Mappings
              },
              CSQModel = (from model in db.CSQActivityReport
                          where model.PhoneReportId == phoneReportID
                          select new CSQModel
                          {
                              // Mappings
                          }).ToList()
          }

您说得对，您需要将CSQModels 用作某种集合，无论是List 还是CSQModel 类型的基本ICollection。您可以根据需要为CallDistributionSummary 编写另一个子查询。

Answer 2

对于每条主记录，您在 2 个单独的子表中各有 3 条记录。除非您添加更多信息，否则您所做的任何联接都会给您 9 条记录（即使您直接转到 T-SQL）。

在 SQL 中执行此操作的一种方法是将表 A 中的记录 1 连接到表 B 中的记录 1，您需要一个索引器来执行此操作。 T-SQL 中的一个选项是在每个子表上使用ROW_NUMBER() 函数并在连接中使用该值。但是，ROW_NUMBER() 还没有扩展到 LINQ。

如果您无法忍受获取重复记录，而只是为每个子结果集执行Distinct() 调用。然后，您可以将其作为两个或 3 个单独的查询来执行。

注意：您可以将其捆绑到存储过程中的 3 个结果集中。您可以轻松地让 EntityFramework 将每个结果反序列化到您的 POCO 中..

            var objCtx = ((IObjectContextAdapter)ctx).ObjectContext;

            using (SqlCommand cmd = ctx.Database.Connection.CreateCommand() as SqlCommand)
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandText = "<your proc here>";

                var param = cmd.CreateParameter();
                param.ParameterName = "@param1";
                param.Value = someValue;
                cmd.Parameters.Add(param);

                await cmd.Connection.OpenAsync();
                using (var reader = await cmd.ExecuteReaderAsync())
                {
                    var results = objCtx.Translate<type1Here>(reader).ToList();
                    reader.NextResult();
                    var results2 = objCtx.Translate<type2Here>(reader).ToList();
                    reader.NextResult();
                    var results3 = objCtx.Translate<type3Here>(reader).ToList();
                    reader.NextResult();
                }
            }

Answer 3

你可以序列化你的对象：

            DataContractJsonSerializer serializer = new DataContractJsonSerializer(GenericObject.GetType());

            MemoryStream ms = new MemoryStream();
            serializer.WriteObject(ms, GenericObject);
            string json = Encoding.UTF8.GetString(ms.ToArray());
            ms.Close();
            return json;