Ejemplos de sintaxis de expresiones de consultas: agrupamiento (LINQ to Entities)

Los ejemplos de este tema muestran cómo se utiliza el método GroupBy para consultar el modelo AdventureWorks Sales con la sintaxis de las expresiones de consulta. El modelo AdventureWorks Sales que se usa en estos ejemplos se crea a partir de las tablas Contact, Address, Product, SalesOrderHeader y SalesOrderDetail en la base de datos de ejemplo AdventureWorks.

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

Option Explicit On
Option Strict On
Imports System.Data.Objects
Imports System.Globalization

using System;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Objects;
using System.Globalization;
using System.Data.EntityClient;
using System.Data.SqlClient;
using System.Data.Common;

Ejemplo

El ejemplo siguiente devuelve los objetos Address agrupados por código postal. Los resultados se proyectan en un tipo anónimo.

Using context As New AdventureWorksEntities
    Dim addresses As ObjectSet(Of Address) = context.Addresses

    Dim query = _
        From adrs In addresses _
        Group adrs By adrs.PostalCode Into g = Group _
        Select New With {.PostalCode = PostalCode, .AddressLine = g}

    For Each addressGroup In query
        Console.WriteLine("Postal Code: {0}", addressGroup.PostalCode)
        For Each adrs In addressGroup.AddressLine
            Console.WriteLine(vbTab & adrs.AddressLine1 & _
                adrs.AddressLine2)
        Next
    Next
End Using

using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    var query =
        from address in context.Addresses
        group address by address.PostalCode into addressGroup
        select new { PostalCode = addressGroup.Key, 
                     AddressLine = addressGroup };

    foreach (var addressGroup in query)
    {
        Console.WriteLine("Postal Code: {0}", addressGroup.PostalCode);
        foreach (var address in addressGroup.AddressLine)
        {
            Console.WriteLine("\t" + address.AddressLine1 +
                address.AddressLine2);
        }
    }
}

Ejemplo

El ejemplo siguiente devuelve los objetos Contact agrupados por la primera letra del apellido del contacto. Los resultados se ordenan también por la primera letra del apellido y se proyectan en un tipo anónimo.

Using context As New AdventureWorksEntities
    Dim contacts As ObjectSet(Of Contact) = context.Contacts

    Dim query = ( _
        From contact In contacts _
        Group By firstLetter = contact.LastName.Substring(0, 1) _
        Into contactGroup = Group _
        Select New With {.FirstLetter = firstLetter, .Names = contactGroup}) _
        .OrderBy(Function(letter) letter.FirstLetter)

    For Each n In query
        Console.WriteLine("Last names that start with the letter '{0}':", _
            n.FirstLetter)
        For Each name In n.Names
            Console.WriteLine(name.LastName)
        Next
    Next
End Using

using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    var query = (
        from contact in context.Contacts
        group contact by contact.LastName.Substring(0, 1) into contactGroup
        select new { FirstLetter = contactGroup.Key, Names = contactGroup }).
            OrderBy(letter => letter.FirstLetter);

    foreach (var contact in query)
    {
        Console.WriteLine("Last names that start with the letter '{0}':",
            contact.FirstLetter);
        foreach (var name in contact.Names)
        {
            Console.WriteLine(name.LastName);
        }
    }
}

Ejemplo

En el ejemplo siguiente se devuelven objetos SalesOrderHeader agrupados por identificador de cliente. También se devuelve el número de ventas para cada cliente.

Using context As New AdventureWorksEntities
    Dim salesOrders As ObjectSet(Of SalesOrderHeader) = context.SalesOrderHeaders

    Dim query = From order In salesOrders _
                    Group order By order.CustomerID Into idGroup = Group, Count()

    For Each group In query
        Console.WriteLine("Customer ID: {0}", group.CustomerID)
        Console.WriteLine("Order Count: {0}", group.Count)

        For Each sale In group.idGroup
            Console.WriteLine("   Sale ID: {0}", sale.SalesOrderID)
        Next

        Console.WriteLine("")
    Next


End Using

using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    var query = from order in context.SalesOrderHeaders
                group order by order.CustomerID into idGroup 
                select new {CustomerID = idGroup.Key, 
                    OrderCount = idGroup.Count(),
                    Sales = idGroup};

    foreach (var orderGroup in query)
    {
        Console.WriteLine("Customer ID: {0}", orderGroup.CustomerID);
        Console.WriteLine("Order Count: {0}", orderGroup.OrderCount);

        foreach (SalesOrderHeader sale in orderGroup.Sales)
        {
            Console.WriteLine("   Sale ID: {0}", sale.SalesOrderID);
        }

        Console.WriteLine("");
    }
}

Vea también

Conceptos

Consultas en LINQ to Entities