public void LinqJoin06()
{
string[] names = { "C#", "VB", "F#" };
var lengths = from name in names select name.Length;
List <Customer> customers = LinqHellper.GetCustomers();
List <Supplier> suppliers = LinqHellper.GetSupplier();
var supplierCusts =
from sup in suppliers
join cust in customers on new { sup.City, sup.Country } equals new { cust.City, cust.Country } into cs
from c in cs.DefaultIfEmpty() //Remove DefaultIfEmpty method call to make this an inner join
orderby sup.SupplierName
select new
{
Country = sup.Country,
City = sup.City,
SupplierName = sup.SupplierName,
CompanyName = c == null ? "(No customers)" : c.CompanyName
};
foreach (var item in supplierCusts)
{
Debug.WriteLine("{0} ({1}, {2}): {3}", item.SupplierName, item.City, item.Country, item.CompanyName);
}
}
//This sample uses Count to return a list of customers and how many orders each has.
public void Count03()
{
List <Customer> customers = LinqHellper.GetCustomers();
var orderCounts =
from cust in customers
select new { cust.CustomerID, OrderCount = cust.Orders.Count() };
foreach (var item in orderCounts)
{
Debug.WriteLine("Custormet Id:" + item.CustomerID + " Order Count:" + item.OrderCount);
}
}
public void LinqJoin01()
{
List <Customer> customers = LinqHellper.GetCustomers();
List <Supplier> suppliers = LinqHellper.GetSupplier();
var custSupJoin =
from sup in suppliers
join cust in customers on sup.Country equals cust.Country
select new { Country = sup.Country, SupplierName = sup.SupplierName, CustomerName = cust.CompanyName };
foreach (var item in custSupJoin)
{
Debug.WriteLine("Country = {0}, Supplier = {1}, Customer = {2}", item.Country, item.SupplierName, item.CustomerName);
}
}
public void LinqTake02()
{
List <Customer> customers = LinqHellper.GetCustomers();
var first3WAOrders = (
from cust in customers
from order in cust.Orders
where cust.Region == "WA"
select new { cust.CustomerID, order.OrderID, order.OrderDate })
.Take(3);
Debug.WriteLine("First 3 orders in WA:");
foreach (var order in first3WAOrders)
{
Debug.WriteLine($"Customer ID: {order.CustomerID} Order ID: {order.OrderID} Order Date: {order.OrderDate}");
}
}
public void LinqSkip02()
{
List <Customer> customers = LinqHellper.GetCustomers();
var waOrders =
from cust in customers
from order in cust.Orders
where cust.Region == "WA"
select new { cust.CustomerID, order.OrderID, order.OrderDate };
var allButFirst2Orders = waOrders.Skip(2);
Debug.WriteLine("All but first 2 orders in WA:");
foreach (var order in allButFirst2Orders)
{
Debug.WriteLine($"Customer ID: {order.CustomerID} Order ID: {order.OrderID} Order Date: {order.OrderDate}");
}
}
public void Restrict04()
{
List <Customer> customers = LinqHellper.GetCustomers();
var waCustomers =
from cust in customers
where cust.Region == "WA"
select cust;
Debug.WriteLine("Customers from Washington and their orders:");
foreach (var customer in waCustomers)
{
Debug.WriteLine("Customer {0}: {1}", customer.CustomerID, customer.CompanyName);
foreach (var order in customer.Orders)
{
Debug.WriteLine(" Order {0}: {1}", order.OrderID, order.OrderDate);
}
}
}
/// <summary>
/// This sample uses Concat to create one sequence that contains the names of all customers and products, including any duplicates.
/// </summary>
public void LinqConcat02()
{
List <Customer> customers = LinqHellper.GetCustomers();
List <Product> products = LinqHellper.GetProducts();
var customerNames =
from cust in customers
select cust.CompanyName;
var productNames =
from prod in products
select prod.ProductName;
var allNames = customerNames.Concat(productNames);
Debug.WriteLine("Customer and product names:");
foreach (var n in allNames)
{
Debug.WriteLine(n);
}
}
public void LinqJoin02()
{
List <Customer> customers = LinqHellper.GetCustomers();
List <Supplier> suppliers = LinqHellper.GetSupplier();
var custSupQuery =
from sup in suppliers
join cust in customers on sup.Country equals cust.Country into cs
select new { Key = sup.Country, Items = cs };
foreach (var item in custSupQuery)
{
Debug.WriteLine(item.Key + ":");
foreach (var element in item.Items)
{
Debug.WriteLine(" " + element.CompanyName);
}
}
}
public void LinqUnion02()
{
List <Product> products = LinqHellper.GetProducts();
List <Customer> customers = LinqHellper.GetCustomers();
var productFirstChars =
from prod in products
select prod.ProductName[0];
var customerFirstChars =
from cust in customers
select cust.CompanyName[0];
var uniqueFirstChars = productFirstChars.Union(customerFirstChars);
Debug.WriteLine("Unique first letters from Product names and Customer names:");
foreach (var ch in uniqueFirstChars)
{
Debug.WriteLine(ch);
}
}
/// <summary>
/// The Except operator produces the set difference between two sequences.
/// The Except operator allocates and returns an enumerable object that captures the arguments passed to the operator. An ArgumentNullException is thrown if any argument is null.
/// </summary>
public void LinqExcept02()
{
List <Product> products = LinqHellper.GetProducts();
List <Customer> customers = LinqHellper.GetCustomers();
var productFirstChars =
from prod in products
select prod.ProductName[0];
var customerFirstChars =
from cust in customers
select cust.CompanyName[0];
var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);
Debug.WriteLine("First letters from Product names, but not from Customer names:");
foreach (var ch in productOnlyFirstChars)
{
Debug.WriteLine(ch);
}
}
public void LinqJoin05()
{
List <Customer> customers = LinqHellper.GetCustomers();
List <Supplier> suppliers = LinqHellper.GetSupplier();
var custSuppliers =
from cust in customers
join sup in suppliers on cust.Country equals sup.Country into ss
from s in ss.DefaultIfEmpty()
orderby cust.CompanyName
select new
{
Country = cust.Country,
CompanyName = cust.CompanyName,
SupplierName = s == null ? "(No suppliers)" : s.SupplierName
};
foreach (var item in custSuppliers)
{
Debug.WriteLine("{0} ({1}): {2}", item.CompanyName, item.Country, item.SupplierName);
}
}
public void LinqJoin04()
{
List <Customer> customers = LinqHellper.GetCustomers();
List <Supplier> suppliers = LinqHellper.GetSupplier();
var supplierCusts =
from sup in suppliers
join cust in customers on sup.Country equals cust.Country into cs
from c in cs.DefaultIfEmpty() // DefaultIfEmpty preserves left-hand elements that have no matches on the right side
orderby sup.SupplierName
select new
{
Country = sup.Country,
CompanyName = c == null ? "(No customers)" : c.CompanyName,
SupplierName = sup.SupplierName
};
foreach (var item in supplierCusts)
{
Debug.WriteLine("{0} ({1}): {2}", item.SupplierName, item.Country, item.CompanyName);
}
}