sql - SQLをLINQ-to-SQLに変換するにはどうすればよいですか？

Question

SELECT     Cities.CityName, Customers.CustomerName, SUM(Bills.Sarees)
FROM       Bills INNER JOIN
                      Customers ON Bills.CustomerID = Customers.CustomerID INNER JOIN
                      Cities ON Customers.CityID = Cities.CityID
Group by CustomerName, CityName

以下のように作成しようとしましたが、groupby句を挿入できません。

 var query = db.Bills.Join(db.Customers, c => c.CustomerID, p => p.CustomerID, (c, p) => new
            {
                c.Customer.CustomerID,
                c.Customer.CustomerName,
                c.Customer.City.CityName,
                c.Customer.Mobile1,
                c.Customer.Mobile2,
                c.Customer.Telephone,
                c.Customer.Email,
                c.Sarees
            });

Answer 1

あなたのSQLを見ると、次のようなものが必要だと思います：

var query = db.Bills
    .Join(db.Customers, b => b.CustomerID, c => c.CustomerID, (b, c) => new
    {
        b.Sarees,
        c.CustomerName,
        c.CityID
    })
    .Join(db.Cities, j => j.CityID, c => c.CityID, (j, c) => new 
    {
        j.Sarees,
        j.CustomerName,
        j.CityID,
        c.CityName
    })
    .GroupBy(o => new { o.CustomerName, o.CityName })
    .Select(o => new { o.Key.CityName, o.Key.CustomerName, Sum = o.Sum(i => i.Sarees) });