Ejemplos de sintaxis de consulta basada en métodos: operadores de conjuntos (LINQ to DataSet)

Los ejemplos de este tema muestran cómo se usan los operadores Distinct, Except, Intersect y Union para realizar operaciones de comparación basadas en valores en conjuntos de filas de datos.Cargar datos en DataSet Vea Comparar DataRows (LINQ to DataSet) para obtener información sobre DataRowComparer.

El método FillDataSet utilizado en estos ejemplos se especifica en Cargar datos en DataSet.

Los ejemplos de este tema utilizan las tablas Contact, Address, Product, SalesOrderHeader y SalesOrderDetail en la base de datos de ejemplo de AdventureWorks.

Los ejemplos de este tema utilizan las siguientes instrucciones using/Imports:

Option Explicit On

Imports System
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

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Data.Common;
using System.Globalization;

Para obtener más información, vea Cómo crear un proyecto LINQ to DataSet en Visual Studio.

Distinct

Ejemplo

Este ejemplo usa el método Distinct para quitar elementos duplicados de una secuencia.

' 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 rows As List(Of DataRow) = New List(Of DataRow)

Dim contacts As DataTable = ds.Tables("Contact")

' Get 100 rows from the Contact table.
Dim query = ( _
    From c In contacts.AsEnumerable() _
    Select c).Take(100)

Dim contactsTableWith100Rows = query.CopyToDataTable()

' Add 100 rows to the list.
For Each row In contactsTableWith100Rows.Rows
    rows.Add(row)
Next

' Create duplicate rows by adding the same 100 rows to the list.
For Each row In contactsTableWith100Rows.Rows
    rows.Add(row)
Next

Dim table = _
        System.Data.DataTableExtensions.CopyToDataTable(Of DataRow)(rows)

' Find the unique contacts in the table.
Dim uniqueContacts = _
    table.AsEnumerable().Distinct(DataRowComparer.Default)

Console.WriteLine("Unique contacts:")
For Each uniqueContact In uniqueContacts
    Console.WriteLine(uniqueContact.Field(Of Integer)("ContactID"))
Next

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

List<DataRow> rows = new List<DataRow>();

DataTable contact = ds.Tables["Contact"];

// Get 100 rows from the Contact table.
IEnumerable<DataRow> query = (from c in contact.AsEnumerable()
                              select c).Take(100);

DataTable contactsTableWith100Rows = query.CopyToDataTable();

// Add 100 rows to the list.
foreach (DataRow row in contactsTableWith100Rows.Rows)
    rows.Add(row);

// Create duplicate rows by adding the same 100 rows to the list.
foreach (DataRow row in contactsTableWith100Rows.Rows)
    rows.Add(row);

DataTable table =
    System.Data.DataTableExtensions.CopyToDataTable<DataRow>(rows);

// Find the unique contacts in the table.
IEnumerable<DataRow> uniqueContacts =
    table.AsEnumerable().Distinct(DataRowComparer.Default);

Console.WriteLine("Unique contacts:");
foreach (DataRow uniqueContact in uniqueContacts)
{
    Console.WriteLine(uniqueContact.Field<Int32>("ContactID"));
}

Except

Ejemplo

Este ejemplo usa el método Except para devolver contactos que aparecen en la primera tabla pero no en la segunda.

' 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 contactTable As DataTable = ds.Tables("Contact")

Dim query1 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("Title") = "Ms." _
    Select contact

Dim query2 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("FirstName") = "Sandra" _
    Select contact

Dim contacts1 = query1.CopyToDataTable()
Dim contacts2 = query2.CopyToDataTable()

' Find the contacts that are in the first 
' table but not the second.
Dim contacts = contacts1.AsEnumerable().Except(contacts2.AsEnumerable(), _
                                              DataRowComparer.Default)

Console.WriteLine("Except of employees tables")

For Each row In contacts
    Console.WriteLine("Id: {0} {1} {2} {3}", _
            row("ContactID"), row("Title"), row("FirstName"), row("LastName"))
Next

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

DataTable contactTable = ds.Tables["Contact"];

// Create two tables.
IEnumerable<DataRow> query1 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("Title") == "Ms."
                              select contact;

IEnumerable<DataRow> query2 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("FirstName") == "Sandra"
                              select contact;


DataTable contacts1 = query1.CopyToDataTable();
DataTable contacts2 = query2.CopyToDataTable();

// Find the contacts that are in the first 
// table but not the second.
var contacts = contacts1.AsEnumerable().Except(contacts2.AsEnumerable(),
                                               DataRowComparer.Default);

Console.WriteLine("Except of employees tables");
foreach (DataRow row in contacts)
{
    Console.WriteLine("Id: {0} {1} {2} {3}",
        row["ContactID"], row["Title"], row["FirstName"], row["LastName"]);
}

Intersect

Ejemplo

Este ejemplo usa el método Intersect para devolver contactos que aparecen en ambas tablas.

' 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 contactTable As DataTable = ds.Tables("Contact")

Dim query1 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("Title") = "Ms." _
    Select contact

Dim query2 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("FirstName") = "Sandra" _
    Select contact

Dim contacts1 = query1.CopyToDataTable()
Dim contacts2 = query2.CopyToDataTable()

Dim contacts = contacts1.AsEnumerable() _
    .Intersect(contacts2.AsEnumerable(), DataRowComparer.Default)

Console.WriteLine("Intersect of employees tables")

For Each row In contacts
    Console.WriteLine("Id: {0} {1} {2} {3}", _
            row("ContactID"), row("Title"), row("FirstName"), row("LastName"))
Next

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

DataTable contactTable = ds.Tables["Contact"];

// Create two tables.
IEnumerable<DataRow> query1 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("Title") == "Ms."
                              select contact;

IEnumerable<DataRow> query2 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("FirstName") == "Sandra"
                              select contact;


DataTable contacts1 = query1.CopyToDataTable();
DataTable contacts2 = query2.CopyToDataTable();

// Find the intersection of the two tables.
var contacts = contacts1.AsEnumerable().Intersect(contacts2.AsEnumerable(),
                                                    DataRowComparer.Default);

Console.WriteLine("Intersection of contacts tables");
foreach (DataRow row in contacts)
{
    Console.WriteLine("Id: {0} {1} {2} {3}",
        row["ContactID"], row["Title"], row["FirstName"], row["LastName"]);
}

Union

Ejemplo

Este ejemplo usa el método Union para devolver contactos únicos de cualquiera de las dos tablas.

' 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 contactTable As DataTable = ds.Tables("Contact")

Dim query1 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("Title") = "Ms." _
    Select contact

Dim query2 = _
    From contact In contactTable.AsEnumerable() _
    Where contact.Field(Of String)("FirstName") = "Sandra" _
    Select contact

Dim contacts1 = query1.CopyToDataTable()
Dim contacts2 = query2.CopyToDataTable()

Dim contacts = contacts1.AsEnumerable().Union(contacts2.AsEnumerable(), _
                                              DataRowComparer.Default)

Console.WriteLine("Union of employees tables")
For Each row In contacts
    Console.WriteLine("Id: {0} {1} {2} {3}", _
            row("ContactID"), row("Title"), row("FirstName"), row("LastName"))
Next

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

// Create two tables.
DataTable contactTable = ds.Tables["Contact"];
IEnumerable<DataRow> query1 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("Title") == "Ms."
                              select contact;

IEnumerable<DataRow> query2 = from contact in contactTable.AsEnumerable()
                              where contact.Field<string>("FirstName") == "Sandra"
                              select contact;


DataTable contacts1 = query1.CopyToDataTable();
DataTable contacts2 = query2.CopyToDataTable();

// Find the union of the two tables.
var contacts = contacts1.AsEnumerable().Union(contacts2.AsEnumerable(),
                                                DataRowComparer.Default);

Console.WriteLine("Union of contacts tables:");
foreach (DataRow row in contacts)
{
    Console.WriteLine("Id: {0} {1} {2} {3}",
        row["ContactID"], row["Title"], row["FirstName"], row["LastName"]);
}

Vea también

Conceptos

Cargar datos en DataSet

Información general sobre operadores de consulta estándar

Otros recursos

Ejemplos de LINQ to DataSet