LINQ到實體合併兩個IQueryable的<AnonymousType>

Question

我有2個查詢其做工精細：

var q = (from c in _context.Wxlogs 

       where (SqlFunctions.DatePart("Month", c.LogDate2) == m3) && (SqlFunctions.DatePart("Year", c.LogDate2) == y1) 
       group c by c.LogDate2 
       into g 
       orderby g.Key 
       let maxTemp = g.Max(c => c.Temp) 
       let minTemp = g.Min(c => c.Temp) 
       let maxHum = g.Max(c => c.Humidity) 
       let minHum = g.Min(c => c.Humidity) 

       select new 
          { 
           LogDate = g.Key, 
           MaxTemp = maxTemp, 
           MaxTempTime = g.FirstOrDefault(c => c.Temp == maxTemp).LogTime, 
           MinTemp = minTemp, 
           MinTempTime = g.FirstOrDefault(c => c.Temp == minTemp).LogTime, 
           MaxHum = maxHum, 
           MaxHumTime = g.FirstOrDefault(c => c.Humidity == maxHum).LogTime, 
           MinHum = minHum, 
           MinHumTime = g.FirstOrDefault(c => c.Humidity == minHum).LogTime, 
          }); 

var r = (from c in _context.Wxlogs 
       where 
        (SqlFunctions.DatePart("Month", c.LogDate2) == m3) && 
        (SqlFunctions.DatePart("Year", c.LogDate2) == y1) 
       group c by c.LogDate2 
        into g 
        orderby g.Key 
        let maxDew = g.Max(c => c.Dew_Point) 
        let minDew = g.Min(c => c.Dew_Point) 
        //let maxWind = g.Max(c=> c.Wind_Gust) 
        let maxRainRate = g.Max(c => c.Rain_rate_now) 
        let maxPres = g.Max(c => c.Barometer) 
        let minPres = g.Min(c => c.Barometer) 

        select new 
           { 
            LogDate = g.Key, 
            MaxRainRateTime = g.FirstOrDefault(c => c.Rain_rate_now == maxRainRate).LogTime, 
            MaxPres = maxPres, 
            MaxPresTime = g.FirstOrDefault(c => c.Barometer == maxPres).LogTime, 
            MinPres = minPres, 
            MinPresTime = g.FirstOrDefault(c => c.Barometer == minPres).LogTime, 
            MinDew = minDew, 
            MinDewTime = g.FirstOrDefault(c => c.Dew_Point == minDew).LogTime, 
            MaxDew = maxDew, 
            MaxDewTime = g.FirstOrDefault(c => c.Dew_Point == maxDew).LogTime, 
            MaxRainRate = maxRainRate, 

           }); 

然而

，當我嘗試給他們使用聯合的結果結合起來，以輸出到WPF datgrid：

var result = r.Union(q); 

以下錯誤拋出的工會：

Error 1 Instance argument: cannot convert from 'System.Linq.IQueryable<AnonymousType#1>' to 'System.Linq.ParallelQuery<AnonymousType#2>' 

我似乎無法找到一種方法，使這項工作和任何幫助將不勝感激。

Answer 1

「聯合」操作將相同類型的兩個序列組合成單個集合（即，消除所有副本）。既然你明顯有兩種不同類型的序列，你不需要聯合操作。它看起來像你想要一個「concat」操作，它只是將兩個序列鏈接在一​​起。你需要的東西，如：

var result = r.Concat<object>(q); 

但是，由於您使用L2E，您的查詢將嘗試獲取服務器上執行。因爲您的服務器不會允許您將合併這兩個查詢（由於不匹配的類型），你需要單獨再執行它們CONCAT客戶端上的序列：

var result = r.AsEnumerable().Concat<object>(q.AsEnumerable()); 

採用AsEnumerable()運行在查詢服務器並將結果提供給客戶端。

因爲事實證明，要序列結合彼此相鄰（即使用您的網格相同的行，但另一組列），你真正想要一個join操作：

var result = from rrow in r.AsEnumerable() 
      join qrow in q.AsEnumerable() on rrow.LogDate equals qrow.LogDate 
      select new { rrow.LogDate, 
          rrow.MaxTemp, rrow.MaxTempTime, 
          rrow.MinTemp, rrow.MinTempTime, 
          rrow.MaxHum, rrow.MaxHumTime, 
          rrow.MinHum, rrow.MinHumTime, 
          qrow.MaxRainRate, qrow.MaxRainRateTime, 
          qrow.MaxPres, qrow.MaxPresTime, 
          qrow.MinPres, qrow.MinPresTime, 
          qrow.MaxDew, qrow.MaxDewTime, 
          qrow.MinDew, qrow.MinDewTime };