Yöntem Tabanlı Sorgu Söz Dizimi Örnekleri: Projeksiyon (LINQ to DataSet)
Bu konudaki örneklerde, yöntem tabanlı sorgu söz dizimi kullanılarak sorgulamak DataSet için ve SelectMany yöntemlerinin nasıl kullanılacağı Select gösterilmektedir.
FillDataSet Bu örneklerde kullanılan yöntem, DataSet'e Veri Yükleme bölümünde belirtilmiştir.
Bu konudaki örneklerde AdventureWorks örnek veritabanındaki Contact, Address, Product, SalesOrderHeader ve SalesOrderDetail tabloları kullanılmıştır.
Bu konudaki örneklerde aşağıdaki using/Imports deyimler kullanılır:
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Globalization;
using System.Linq;
using System.Windows.Forms;
Option Explicit On
Imports System.Linq
Imports System.Linq.Expressions
Imports System.Collections.Generic
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.Common
Imports System.Globalization
Daha fazla bilgi için bkz . Nasıl yapılır: Visual Studio'da LINQ to DataSet Projesi Oluşturma.
Seç
Örnek
Bu örnek, , ve özelliklerini bir dizi anonim türe yansıtmak Nameiçin yöntemini kullanırSelect.ListPrice ProductNumber Özellik ListPrice , sonuçta elde edilen Price türde olarak da yeniden adlandırılır.
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable products = ds.Tables["Product"];
var query = products.AsEnumerable().
Select(product => new
{
ProductName = product.Field<string>("Name"),
ProductNumber = product.Field<string>("ProductNumber"),
Price = product.Field<decimal>("ListPrice")
});
Console.WriteLine("Product Info:");
foreach (var productInfo in query)
{
Console.WriteLine("Product name: {0} Product number: {1} List price: ${2} ",
productInfo.ProductName, productInfo.ProductNumber, productInfo.Price);
}
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim products As DataTable = ds.Tables("Product")
Dim query = products.AsEnumerable() _
.Select(Function(product As DataRow) New With _
{ _
.ProductName = product.Field(Of String)("Name"), _
.ProductNumber = product.Field(Of String)("ProductNumber"), _
.Price = product.Field(Of Decimal)("ListPrice") _
})
Console.WriteLine("Product Info:")
For Each product In query
Console.Write("Product name: " & product.ProductName)
Console.Write("Product number: " & product.ProductNumber)
Console.WriteLine("List price: $ " & product.Price)
Next
Selectmany
Örnek
Bu örnekte, 500,00'den küçük olan tüm siparişleri TotalDue seçmek için yöntemi kullanılırSelectMany.
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
var contacts = ds.Tables["Contact"].AsEnumerable();
var orders = ds.Tables["SalesOrderHeader"].AsEnumerable();
var query =
contacts.SelectMany(
contact => orders.Where(order =>
(contact.Field<Int32>("ContactID") == order.Field<Int32>("ContactID"))
&& order.Field<decimal>("TotalDue") < 500.00M)
.Select(order => new
{
ContactID = contact.Field<int>("ContactID"),
LastName = contact.Field<string>("LastName"),
FirstName = contact.Field<string>("FirstName"),
OrderID = order.Field<int>("SalesOrderID"),
Total = order.Field<decimal>("TotalDue")
}));
foreach (var smallOrder in query)
{
Console.WriteLine("Contact ID: {0} Name: {1}, {2} Order ID: {3} Total Due: ${4} ",
smallOrder.ContactID, smallOrder.LastName, smallOrder.FirstName,
smallOrder.OrderID, smallOrder.Total);
}
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim contacts = ds.Tables("Contact").AsEnumerable()
Dim orders = ds.Tables("SalesOrderHeader").AsEnumerable()
Dim query = _
contacts.SelectMany( _
Function(contact) orders.Where(Function(order) _
(contact.Field(Of Int32)("ContactID") = order.Field(Of Int32)("ContactID")) _
And order.Field(Of Decimal)("TotalDue") < 500D) _
.Select(Function(order) New With _
{ _
.ContactID = contact.Field(Of Integer)("ContactID"), _
.LastName = contact.Field(Of String)("LastName"), _
.FirstName = contact.Field(Of String)("FirstName"), _
.OrderID = order.Field(Of Integer)("SalesOrderID"), _
.Total = order.Field(Of Decimal)("TotalDue") _
}))
For Each smallOrder In query
Console.Write("ContactID: " & smallOrder.ContactID)
Console.Write(" Name: " & smallOrder.LastName & ", " & smallOrder.FirstName)
Console.Write(" Order ID: " & smallOrder.OrderID)
Console.WriteLine(" Total Due: $" & smallOrder.Total)
Next
Örnek
Bu örnekte, 1 Ekim 2002 veya sonraki bir tarihte siparişin yapıldığı tüm siparişleri seçmek için yöntemi kullanılır SelectMany .
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
var contacts = ds.Tables["Contact"].AsEnumerable();
var orders = ds.Tables["SalesOrderHeader"].AsEnumerable();
var query =
contacts.SelectMany(
contact => orders.Where(order =>
(contact.Field<Int32>("ContactID") == order.Field<Int32>("ContactID"))
&& order.Field<DateTime>("OrderDate") >= new DateTime(2002, 10, 1))
.Select(order => new
{
ContactID = contact.Field<int>("ContactID"),
LastName = contact.Field<string>("LastName"),
FirstName = contact.Field<string>("FirstName"),
OrderID = order.Field<int>("SalesOrderID"),
OrderDate = order.Field<DateTime>("OrderDate")
}));
foreach (var order in query)
{
Console.WriteLine("Contact ID: {0} Name: {1}, {2} Order ID: {3} Order date: {4:d} ",
order.ContactID, order.LastName, order.FirstName,
order.OrderID, order.OrderDate);
}
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim contacts = ds.Tables("Contact").AsEnumerable()
Dim orders = ds.Tables("SalesOrderHeader").AsEnumerable()
Dim query = _
contacts.SelectMany( _
Function(contact) orders.Where(Function(order) _
(contact.Field(Of Int32)("ContactID") = order.Field(Of Int32)("ContactID")) _
And order.Field(Of DateTime)("OrderDate") >= New DateTime(2002, 10, 1)) _
.Select(Function(order) New With _
{ _
.ContactID = contact.Field(Of Integer)("ContactID"), _
.LastName = contact.Field(Of String)("LastName"), _
.FirstName = contact.Field(Of String)("FirstName"), _
.OrderID = order.Field(Of Integer)("SalesOrderID"), _
.OrderDate = order.Field(Of DateTime)("OrderDate") _
}))
For Each order In query
Console.Write("Contact ID: " & order.ContactID)
Console.Write(" Name: " & order.LastName & ", " & order.FirstName)
Console.Write(" Order ID: " & order.OrderID)
Console.WriteLine(" Order date: {0:d}", order.OrderDate)
Next