LINQ to SQL - Grouping by hours

Hi, How can I group result of a LINQ to SQL query by hours considering that the column type is DateTime?

From stackoverflow

• Here's a solution for technical hours (context-less).

  var query = myDC.Orders
      .GroupBy(x => x.OrderDate.Hour)
      .Select(g => new {
          Hour = g.Key,
          Amount = g.Sum(x => x.OrderAmount)
      });
  

  Which generates this:

  SELECT SUM([t1].[OrderAmount]) AS [Amount], [t1].[value] AS [Hour]
  FROM (
      SELECT DATEPART(Hour, [t0].[OrderDate]) AS [value], [t0].[OrderAmount]
      FROM [dbo].[Orders] AS [t0]
      ) AS [t1]
  GROUP BY [t1].[value]
  

  ---

  Here's a solution for business hours (context-ful) .

  DateTime zeroDate = new DateTime(2008, 1, 1);
  
  var query = myDC.Orders
      .GroupBy(x => System.Data.Linq.SqlClient.SqlMethods.DateDiffHour(zeroDate, x.OrderDate)
      )
      .Select(g => new { Hours = g.Key, Amount = g.Sum(x => x.OrderAmount) })
      .Select(x => new { Hour = zeroDate.AddHours(x.Hours), Amount = x.Amount});
  

  Which generates this:

  SELECT DATEADD(ms, (CONVERT(BigInt,(CONVERT(Float,[t2].[value2])) * 3600000)) % 86400000, DATEADD(day, (CONVERT(BigInt,(CONVERT(Float,[t2].[value2])) * 3600000)) / 86400000, @p1)) AS [Hour], [t2].[value] AS [Amount]
  FROM (
      SELECT SUM([t1].[OrderAmount]) AS [value], [t1].[value] AS [value2]
      FROM (
          SELECT DATEDIFF(Hour, @p0, [t0].[OrderDate]) AS [value], [t0].[OrderAmount]
          FROM [dbo].[Orders] AS [t0]
          ) AS [t1]
      GROUP BY [t1].[value]
      ) AS [t2]
  

  ---

  Ugh - that bigint/float/milliseconds stuff is ugly and hard to verify. I prefer doing the addition back on the client side:

  var results = myDC.Orders
      .GroupBy(x => System.Data.Linq.SqlClient.SqlMethods.DateDiffHour(zeroDate, x.OrderDate)
      )
      .Select(g => new { Hours = g.Key, Amount = g.Sum(x => x.OrderAmount) })
      .ToList()
      .Select(x => new { Hour = zeroDate.AddHours(x.Hours), Amount = x.Amount});
  

  Which generates this:

  SELECT SUM([t1].[OrderAmount]) AS [Amount], [t1].[value] AS [Hours]
  FROM (
      SELECT DATEDIFF(Hour, @p0, [t0].[OrderDate]) AS [value], [t0].[OrderAmount]
      FROM [dbo].[Orders] AS [t0]
      ) AS [t1]
  GROUP BY [t1].[value]
  

  ---

  And here's a third way of doing the contextful hours. This one is very c# friendly, but there's string logic in the database (yuck).

  var query = myDC.Orders
      .GroupBy(x => new DateTime(x.OrderDate.Year, x.OrderDate.Month, x.OrderDate.Day, x.OrderDate.Hour, 0, 0))
      .Select(g => new { Hour = g.Key, Amount = g.Sum(x => x.OrderAmount) });
  

  Which generates

  SELECT SUM([t1].[OrderAmount]) AS [Amount], [t1].[value] AS [Hour]
  FROM (
      SELECT CONVERT(DATETIME, (CONVERT(NCHAR(4), DATEPART(Year, [t0].[OrderDate])) + ('-' + (CONVERT(NCHAR(2), DATEPART(Month, [t0].[OrderDate])) + ('-' + CONVERT(NCHAR(2), DATEPART(Day, [t0].[OrderDate])))))) + (' ' + (CONVERT(NCHAR(2), DATEPART(Hour, [t0].[OrderDate])) + (':' + (CONVERT(NCHAR(2), @p0) + (':' + CONVERT(NCHAR(2), @p1)))))), 120) AS [value], [t0].[OrderAmount]
      FROM [dbo].[Orders] AS [t0]
      ) AS [t1]
  GROUP BY [t1].[value]