将WHERE语句添加到LINQ lambda表达式

Question

The two tables I'm working with here are built like this:

Users Table                             PurchaseLog Table

ID| LDAP| FNAME| LNAME|                 ID| UserID| PurchaseID | LOCATION |TIME

I'm trying to build a query that gets me back each user and the number of purchases they have. The model I'm trying to fill:

public class UserPurchaseCount{
    public string LDAP {get; set;}
    public int Count {get; set;}
}

This SQL query I wrote appears to be returning the correct results,

Select Users.LDAP, count(*) as Purchases
FROM Users
JOIN PurchaseLog ON PurchaseLog.UserId=Users.ID
WHERE Users.FName NOT LIKE '%name%'
AND PurchaseLog.CreatedDate <= 'some end date'
AND Purchase.CreatedDate >= 'some start date'
GROUP BY Users.LDAP

I suck at lambdas, but I like them and want to get a better understanding of them. Here's what I've got so far:

        var items = db.PurchaseLogs
                .Join(db.Users, usr => usr.UserId, x => x.ID, (usr, x) => new { usr, x })
                .GroupBy(y => new { y.x.LDAP})
                //.Where(i => i.CreatedDate >= startDate)
                //.Where(i => i.CreatedDate <= endDate)
                //.Where(i => i.FName.Contains("Guy1", StringComparison.CurrentCultureIgnoreCase) == false)
                .Select(g => new
                {
                    g.Key.LDAP,
                    Count = g.Count()
                })

                .ToList();

This lambda expression works. When I uncomment the WHERE clauses, the compiler throws up in my face.

Error   6   'System.Linq.IGrouping<AnonymousType#2,AnonymousType#3>' does not contain a definition for 'FName'...

Answer 1

Don't group before apply the conditions:

var items =db.PurchaseLogs
             .Join(db.Users, usr => usr.UserId, x => x.ID, (usr, x) => new { usr, x })
             .Where(i => i.user.CreatedDate >= startDate)
             .Where(i => i.user.CreatedDate <= endDate)
             .Where(i => !i.x.FName.Contains("Guy1"))
             .GroupBy(y => new { y.x.LDAP})
             .Select(g => new
                         {
                          g.Key.LDAP,
                           Count = g.Count()
                          })

             .ToList();