static void Main(string[] args)
{
using (var db = new NutshellContextDataContext())
{
var t = Enumerable.Empty<int>();
}
WhereSample();
WhereSample2();
TakeWhileSample();
Projecting();
Hierarchy();
SubQuery();
SelectManySample();
SelectManySample2();
JoinSample();
}
static void ProjectionFromDB()
{
XDocument doc;
using (var db = new NutshellContextDataContext())
{
var custList = (from c in db.Customers
select new { Name = c.Name, ID = c.ID, Count = c.Purchases.Count }).ToList();
doc = new XDocument(new XStreamingElement("Customers",
from c in custList
select new XElement("Customer", new XAttribute("id", c.ID),
new XElement("Name", c.Name),
new XElement("Buys", c.Count))
));
Console.WriteLine(doc.ToString());
}
}
private static void JoinSample()
{
using (var db = new NutshellContextDataContext())
{
var customers = db.Customers.ToArray();
var purchases = db.Purchases.ToArray();
var slowQuery =
from c in customers
from p in purchases
where c.ID == p.CustomerID
select c.Name + " bought a " + p.Description;
var fastQuery =
from c in customers
join p in purchases on c.ID equals p.CustomerID
select c.Name + " bought a " + p.Description;
}
}
private static void SubQuery()
{
using (var db = new NutshellContextDataContext())
{
// kind of left outer join
var queryLOJ =
from c in db.Customers
select new
{
c.Name,
Purchases = from p in c.Purchases
where p.CustomerID == c.ID && p.Price > 600
select new { p.Description, p.Price }
};
// kind of inner join (sql becomes left outer join with exists)
var queryRIJ =
from c in db.Customers
let hpur = from p in c.Purchases where p.Price > 600 select new { p.Description, p.Price }
where hpur.Any()
select new { c.Name, Purchases = hpur };
//var queryJKL =
// from p in db.Purchases
// group g by p.CustomerID as ff
foreach (var cname in queryLOJ)
{
Console.WriteLine($"Customer: {cname.Name}");
foreach (var pur in cname.Purchases)
{
Console.WriteLine($"\t{pur.Price}");
}
}
}
}
static void Main(string[] args)
{
Expression <Func <Customer, bool> > first = (c) => c.ID == 1; // ->LambdaExpression -> Expression
Console.WriteLine(first.Body.NodeType);
Console.WriteLine(((BinaryExpression)first.Body).Left);
using (var db = new NutshellContextDataContext())
{
var query = from c in db.Customers
where c.Name.Contains("a")
orderby c.Name.Length
select c.Name.ToUpper();
System.Console.WriteLine(query);
System.Console.WriteLine("Result: " + TS(query));
DataLoadOptions opt = new DataLoadOptions();
//opt.AssociateWith<Customer>(c => c.Purchases.Where(p => p.Price > 900));
opt.LoadWith <Customer>(c => c.Purchases); //force eager loading
db.LoadOptions = opt;
var q2 = from c in db.Customers
select
from p in c.Purchases
select new { c.Name, p.Price };
//System.Console.WriteLine(q2);
foreach (var c1 in q2)
{
foreach (var namePrice in c1)
{
Console.WriteLine(namePrice);
}
//Console.WriteLine($"{namePrice.Name} +spent {namePrice.Price}");
}
}
}
