Sorgu İfadesi Söz Dizimi Örnekleri: Projeksiyon İşlemi (LINQ to DataSet)

Bu konudaki örnekler, sorgu ifadesi söz dizimini kullanarak bir Select sorgulamak için SelectMany ve DataSet yöntemlerinin nasıl kullanılacağını gösterir.

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 yöntemi kullanarak Product tablosundaki tüm satırları döndürür ve ürün adlarını görüntüler.

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable products = ds.Tables["Product"];

IEnumerable<DataRow> query =
    from product in products.AsEnumerable()
    select product;

Console.WriteLine("Product Names:");
foreach (DataRow p in query)
{
    Console.WriteLine(p.Field<string>("Name"));
}

' 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 = From product In products.AsEnumerable() _
            Select product
Console.WriteLine("Product Names:")
For Each p In query
    Console.WriteLine(p.Field(Of String)("Name"))
Next

Örnek

Bu örnek yalnızca ürün adlarının bir dizisini döndürmek için kullanır Select .

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable products = ds.Tables["Product"];

IEnumerable<string> query =
    from product in products.AsEnumerable()
    select product.Field<string>("Name");

Console.WriteLine("Product Names:");
foreach (string productName in query)
{
    Console.WriteLine(productName);
}

' 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 = From product In products.AsEnumerable() _
            Select product.Field(Of String)("Name")

Console.WriteLine("Product Names:")
For Each productName In query
    Console.WriteLine(productName)
Next

SelectMany

Örnek

Bu örnekte From …, … (SelectMany yönteminin eşdeğeri) kullanılarak TotalDue 500,00'den küçük olan tüm siparişler seçilir.

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable contacts = ds.Tables["Contact"];
DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from contact in contacts.AsEnumerable()
    from order in orders.AsEnumerable()
    where contact.Field<int>("ContactID") == order.Field<int>("ContactID")
        && order.Field<decimal>("TotalDue") < 500.00M
    select 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 As DataTable = ds.Tables("Contact")
Dim orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From contact In contacts.AsEnumerable() _
    From order In orders.AsEnumerable() _
    Where (contact.Field(Of Integer)("ContactID") = _
        order.Field(Of Integer)("ContactID")) _
        And (order.Field(Of Decimal)("TotalDue") < 500D) _
    Select 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"), _
        .TotalDue = order.Field(Of Decimal)("TotalDue") _
    }

For Each smallOrder In query
    Console.Write("ContactID: " & smallOrder.ContactID)
    Console.Write(" Name: {0}, {1}", smallOrder.LastName, _
                       smallOrder.FirstName)
    Console.Write(" OrderID: " & smallOrder.OrderID)
    Console.WriteLine(" TotalDue: $" & smallOrder.TotalDue)
Next

Örnek

Bu örnekte, From …, … (SelectMany yönteminin eşdeğeri), siparişin 1 Ekim 2002 veya daha sonraki bir tarihte yapıldığı tüm siparişleri seçmek için kullanılır.

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable contacts = ds.Tables["Contact"];
DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from contact in contacts.AsEnumerable()
    from order in orders.AsEnumerable()
    where contact.Field<int>("ContactID") == order.Field<int>("ContactID") &&
        order.Field<DateTime>("OrderDate") >= new DateTime(2002, 10, 1)
    select 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 As DataTable = ds.Tables("Contact")
Dim orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From contact In contacts.AsEnumerable() _
    From order In orders.AsEnumerable() _
    Where contact.Field(Of Integer)("ContactID") = order.Field(Of Integer)("ContactID") And _
        order.Field(Of DateTime)("OrderDate") >= New DateTime(2002, 10, 1) _
    Select 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

Örnek

Bu örnek, sipariş toplamının 10000,00'den büyük olduğu tüm siparişleri seçmek için bir From …, … (yöntemin SelectMany eşdeğeri) kullanır ve toplamı iki kez istememek için atamayı kullanır From .

// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);

DataTable contacts = ds.Tables["Contact"];
DataTable orders = ds.Tables["SalesOrderHeader"];

var query =
    from contact in contacts.AsEnumerable()
    from order in orders.AsEnumerable()
    let total = order.Field<decimal>("TotalDue")
    where contact.Field<int>("ContactID") == order.Field<int>("ContactID") &&
          total >= 10000.0M
    select new
    {
        ContactID = contact.Field<int>("ContactID"),
        LastName = contact.Field<string>("LastName"),
        OrderID = order.Field<int>("SalesOrderID"),
        total
    };
foreach (var order in query)
{
    Console.WriteLine($"Contact ID: {order.ContactID} Last name: {order.LastName} Order ID: {order.OrderID} Total: {order.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 As DataTable = ds.Tables("Contact")
Dim orders As DataTable = ds.Tables("SalesOrderHeader")

Dim query = _
    From contact In contacts.AsEnumerable() _
    From order In orders.AsEnumerable() _
    Let total = order.Field(Of Decimal)("TotalDue") _
    Where contact.Field(Of Integer)("ContactID") = order.Field(Of Integer)("ContactID") And _
        total >= 10000D _
    Select New With _
        { _
           .ContactID = contact.Field(Of Integer)("ContactID"), _
           .LastName = contact.Field(Of String)("LastName"), _
           .OrderID = order.Field(Of Integer)("SalesOrderID"), _
           .OrderDate = order.Field(Of DateTime)("OrderDate"), _
           total _
        }

For Each order In query
    Console.Write("Contact ID: " & order.ContactID)
    Console.Write(" Last Name: " & order.LastName)
    Console.Write(" Order ID: " & order.OrderID)
    Console.WriteLine(" Total: $" & order.total)
Next

Ayrıca bkz.

• DataSet’e Veri Yükleme
• LINQ to DataSet Örnekleri
• Standart Sorgu İşleçlerine Genel Bakış (C#)
• Standart Sorgu İşleçlerine Genel Bakış (Visual Basic)