Sql server 如何在linq中编写此SQL平均查询

下面是我希望运行的SQL：

DECLARE @StartDt DATETIME, @EndDt DATETIME
SET @StartDt='2009-01-01'
SET @EndDt='2010-06-01'

SELECT  
AVG(DATEDIFF(day, CreatedDt, CompletedDt)) 
AVG(DATEDIFF(day, CreatedDt, ComplianceDt)) 
FROM MyTable
WHERE RequestDt BETWEEN @StartDt AND @EndDt

这可以用Linq（C#）表示并在数据库上运行吗？

DateTime startDt=new DateTime（2009,1,1）；
DateTime startDt = new DateTime(2009, 1, 1);
DateTime endDt = new DateTme(2010, 6, 1);

var query = dc.MyTables
  .Where(x => startDt <= x.RequestDate && x.RequestDt <= endDt)
  .GroupBy(x => 1)  //unsure about this group by
  .Select(g => new
  {
    FirstAvg = g.Average(x =>
      SqlMethods.DateDiffDay(x.CreatedDt, x.CompletedDt)),
    SecondAvg = g.Average(x =>
      SqlMethods.DateDiffDay(x.CreatedDt, x.ComplianceDt))
  });

var row = query.Single();

DateTime endDt=新的dateme（2010,6,1）；
var query=dc.MyTables
.其中（x=>startDt new
{
FirstAvg=g.平均值（x=>
SqlMethods.DateDiffDay（x.CreatedDt，x.CompletedDt）），
SecondAvg=g.平均值（x=>
SqlMethods.DateDiffDay（x.CreatedDt，x.ComplianceDt））
});
var row=query.Single（）；

Easy并不是我唯一看重的质量。