LINQ - Set data
Dataset menawarkan representasi data yang sangat berguna dalam memori dan digunakan untuk beragam aplikasi berbasis data. LINQ ke Dataset sebagai salah satu teknologi LINQ ke ADO. NET memfasilitasi melakukan kueri pada data Dataset dengan cara yang tidak merepotkan dan meningkatkan produktivitas.
Pengenalan LINQ ke Set Data
LINQ ke Dataset telah membuat tugas kueri menjadi sederhana untuk pengembang. Mereka tidak perlu menulis kueri dalam bahasa kueri tertentu, tetapi hal yang sama dapat ditulis dalam bahasa pemrograman. LINQ ke Kumpulan Data juga dapat digunakan untuk membuat kueri tempat data dikonsolidasikan dari berbagai sumber data. Ini juga tidak memerlukan penyedia LINQ seperti LINQ ke SQL dan LINQ ke XML untuk mengakses data dari dalam koleksi memori.
Di bawah ini adalah contoh sederhana dari query LINQ ke Dataset dimana sumber data diperoleh terlebih dahulu dan kemudian dataset diisi dengan dua tabel data. Hubungan dibuat antara tabel dan kueri LINQ dibuat terhadap kedua tabel melalui klausa gabungan. Akhirnya, foreach loop digunakan untuk menampilkan hasil yang diinginkan.
C #
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LINQtoDataset {
class Program {
static void Main(string[] args) {
string connectString = System.Configuration.ConfigurationManager.ConnectionStrings["LinqToSQLDBConnectionString"].ToString();
string sqlSelect = "SELECT * FROM Department;" + "SELECT * FROM Employee;";
// Create the data adapter to retrieve data from the database
SqlDataAdapter da = new SqlDataAdapter(sqlSelect, connectString);
// Create table mappings
da.TableMappings.Add("Table", "Department");
da.TableMappings.Add("Table1", "Employee");
// Create and fill the DataSet
DataSet ds = new DataSet();
da.Fill(ds);
DataRelation dr = ds.Relations.Add("FK_Employee_Department",
ds.Tables["Department"].Columns["DepartmentId"],
ds.Tables["Employee"].Columns["DepartmentId"]);
DataTable department = ds.Tables["Department"];
DataTable employee = ds.Tables["Employee"];
var query = from d in department.AsEnumerable()
join e in employee.AsEnumerable()
on d.Field<int>("DepartmentId") equals
e.Field<int>("DepartmentId")
select new {
EmployeeId = e.Field<int>("EmployeeId"),
Name = e.Field<string>("Name"),
DepartmentId = d.Field<int>("DepartmentId"),
DepartmentName = d.Field<string>("Name")
};
foreach (var q in query) {
Console.WriteLine("Employee Id = {0} , Name = {1} , Department Name = {2}",
q.EmployeeId, q.Name, q.DepartmentName);
}
Console.WriteLine("\nPress any key to continue.");
Console.ReadKey();
}
}
}VB
Imports System.Data.SqlClient
Imports System.Linq
Module LinqToDataSet
Sub Main()
Dim connectString As String = System.Configuration.ConfigurationManager.ConnectionStrings("LinqToSQLDBConnectionString").ToString()
Dim sqlSelect As String = "SELECT * FROM Department;" + "SELECT * FROM Employee;"
Dim sqlCnn As SqlConnection = New SqlConnection(connectString)
sqlCnn.Open()
Dim da As New SqlDataAdapter
da.SelectCommand = New SqlCommand(sqlSelect, sqlCnn)
da.TableMappings.Add("Table", "Department")
da.TableMappings.Add("Table1", "Employee")
Dim ds As New DataSet()
da.Fill(ds)
Dim dr As DataRelation = ds.Relations.Add("FK_Employee_Department", ds.Tables("Department").Columns("DepartmentId"), ds.Tables("Employee").Columns("DepartmentId"))
Dim department As DataTable = ds.Tables("Department")
Dim employee As DataTable = ds.Tables("Employee")
Dim query = From d In department.AsEnumerable()
Join e In employee.AsEnumerable() On d.Field(Of Integer)("DepartmentId") Equals
e.Field(Of Integer)("DepartmentId")
Select New Person With { _
.EmployeeId = e.Field(Of Integer)("EmployeeId"),
.EmployeeName = e.Field(Of String)("Name"),
.DepartmentId = d.Field(Of Integer)("DepartmentId"),
.DepartmentName = d.Field(Of String)("Name")
}
For Each e In query
Console.WriteLine("Employee Id = {0} , Name = {1} , Department Name = {2}", e.EmployeeId, e.EmployeeName, e.DepartmentName)
Next
Console.WriteLine(vbLf & "Press any key to continue.")
Console.ReadKey()
End Sub
Class Person
Public Property EmployeeId As Integer
Public Property EmployeeName As String
Public Property DepartmentId As Integer
Public Property DepartmentName As String
End Class
End ModuleKetika kode C # atau VB di atas dikompilasi dan dijalankan, itu menghasilkan hasil sebagai berikut -
Employee Id = 1, Name = William, Department Name = Account
Employee Id = 2, Name = Benjamin, Department Name = Account
Employee Id = 3, Name = Miley, Department Name = Sales
Press any key to continue.Membuat Kueri Set Data menggunakan LinQ ke Set Data
Sebelum mulai membuat kueri Set Data menggunakan LINQ ke Set Data, sangat penting untuk memuat data ke Set Data dan ini dilakukan dengan menggunakan kelas DataAdapter atau dengan LINQ ke SQL. Perumusan kueri yang menggunakan LINQ ke Kumpulan Data sangat mirip dengan merumuskan kueri dengan menggunakan LINQ bersama sumber data lain yang mendukung LINQ.
Kueri Tabel Tunggal
Dalam kueri tabel tunggal berikut ini, semua pesanan online dikumpulkan dari SalesOrderHeaderTtable lalu ID pesanan, tanggal pesanan serta nomor pesanan ditampilkan sebagai output.
C#
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LinqToDataset {
class SingleTable {
static void Main(string[] args) {
string connectString = System.Configuration.ConfigurationManager.ConnectionStrings["LinqToSQLDBConnectionString"].ToString();
string sqlSelect = "SELECT * FROM Department;";
// Create the data adapter to retrieve data from the database
SqlDataAdapter da = new SqlDataAdapter(sqlSelect, connectString);
// Create table mappings
da.TableMappings.Add("Table", "Department");
// Create and fill the DataSet
DataSet ds = new DataSet();
da.Fill(ds);
DataTable department = ds.Tables["Department"];
var query = from d in department.AsEnumerable()
select new {
DepartmentId = d.Field<int>("DepartmentId"),
DepartmentName = d.Field<string>("Name")
};
foreach (var q in query) {
Console.WriteLine("Department Id = {0} , Name = {1}",
q.DepartmentId, q.DepartmentName);
}
Console.WriteLine("\nPress any key to continue.");
Console.ReadKey();
}
}
}VB
Imports System.Data.SqlClient
Imports System.Linq
Module LinqToDataSet
Sub Main()
Dim connectString As String = System.Configuration.ConfigurationManager.ConnectionStrings("LinqToSQLDBConnectionString").ToString()
Dim sqlSelect As String = "SELECT * FROM Department;"
Dim sqlCnn As SqlConnection = New SqlConnection(connectString)
sqlCnn.Open()
Dim da As New SqlDataAdapter
da.SelectCommand = New SqlCommand(sqlSelect, sqlCnn)
da.TableMappings.Add("Table", "Department")
Dim ds As New DataSet()
da.Fill(ds)
Dim department As DataTable = ds.Tables("Department")
Dim query = From d In department.AsEnumerable()
Select New DepartmentDetail With {
.DepartmentId = d.Field(Of Integer)("DepartmentId"),
.DepartmentName = d.Field(Of String)("Name")
}
For Each e In query
Console.WriteLine("Department Id = {0} , Name = {1}", e.DepartmentId, e.DepartmentName)
Next
Console.WriteLine(vbLf & "Press any key to continue.")
Console.ReadKey()
End Sub
Public Class DepartmentDetail
Public Property DepartmentId As Integer
Public Property DepartmentName As String
End Class
End ModuleKetika kode C # atau VB di atas dikompilasi dan dijalankan, itu menghasilkan hasil sebagai berikut -
Department Id = 1, Name = Account
Department Id = 2, Name = Sales
Department Id = 3, Name = Pre-Sales
Department Id = 4, Name = Marketing
Press any key to continue.