Compartir a través de

Ejemplos de sintaxis de expresiones de consulta: agrupación

Los ejemplos de este tema muestran cómo usar el GroupBy método para consultar el modelo de ventas de AdventureWorks mediante la sintaxis de expresiones de consulta. El modelo AdventureWorks Sales usado en estos ejemplos se compila a partir de las tablas Contact, Address, Product, SalesOrderHeader y SalesOrderDetail de la base de datos de ejemplo AdventureWorks.

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

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;


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

Ejemplo 1

En el ejemplo siguiente se devuelven Address objetos agrupados por código postal. Los resultados se proyectan en un tipo anónimo.

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

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

Ejemplo 2

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

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 '{contact.FirstLetter}':");
        foreach (var name in contact.Names)
        {
            Console.WriteLine(name.LastName);
        }
    }
}

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

Ejemplo 3

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

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($"Customer ID: {orderGroup.CustomerID}");
        Console.WriteLine($"Order Count: {orderGroup.OrderCount}");

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

        Console.WriteLine("");
    }
}

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

Consulte también