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Method-Based Sorgu Söz Dizimi Örnekleri: Projeksiyon (LINQ to DataSet)

Bu konudaki örnekler, Select ve SelectMany yöntemlerinin, yöntem tabanlı sorgu söz dizimini kullanarak bir DataSet sorgulamak için nasıl kullanılacağını göstermektedir.

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 deyimleri 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, Select yöntemini kullanarak Name, ProductNumber ve ListPrice özelliklerini anonim türlerin bir dizisine yansıtır. Özellik ListPrice, oluşan türde Price 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: {productInfo.ProductName} Product number: {productInfo.ProductNumber} List price: ${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 örnek, SelectMany yöntemini kullanarak TotalDue 500,00'den küçük olan tüm siparişleri seçer.

// 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

Ayrıca bkz.

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