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Query Expression Syntax Examples: Navigating Relationships

  • Article
  • 09/15/2021

Navigation properties in the Entity Framework are shortcut properties used to locate the entities at the ends of an association. Navigation properties allow a user to navigate from one entity to another, or from one entity to related entities through an association set. This topic provides examples in query expression syntax of how to navigate relationships through navigation properties in LINQ to Entities queries.

The AdventureWorks Sales Model used in these examples is built from the Contact, Address, Product, SalesOrderHeader, and SalesOrderDetail tables in the AdventureWorks sample database.

The examples in this topic use the following using/Imports statements:

C# 
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;

Example 1

The following example uses the Select method to get all the contact IDs and the sum of the total due for each contact whose last name is "Zhou". The Contact.SalesOrderHeader navigation property is used to get the collection of SalesOrderHeader objects for each contact. The Sum method uses the Contact.SalesOrderHeader navigation property to sum the total due of all the orders for each contact.

C# 
string lastName = "Zhou";
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    ObjectSet<Contact> contacts = context.Contacts;

    var ordersQuery = from contact in contacts
                      where contact.LastName == lastName
                      select new
                      {
                          ContactID = contact.ContactID,
                          Total = contact.SalesOrderHeaders.Sum(o => o.TotalDue)
                      };

    foreach (var contact in ordersQuery)
    {
        Console.WriteLine($"Contact ID: {contact.ContactID} Orders total: {contact.Total}");
    }
}

Example 2

The following example gets all the orders of the contacts whose last name is "Zhou". The Contact.SalesOrderHeader navigation property is used to get the collection of SalesOrderHeader objects for each contact. The contact's name and orders are returned in an anonymous type.

C# 
string lastName = "Zhou";
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    ObjectSet<Contact> contacts = context.Contacts;

    var ordersQuery = from contact in contacts
                      where contact.LastName == lastName
                      select new { LastName = contact.LastName, Orders = contact.SalesOrderHeaders };

    foreach (var order in ordersQuery)
    {
        Console.WriteLine($"Name: {order.LastName}");
        foreach (SalesOrderHeader orderInfo in order.Orders)
        {
            Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}",
                orderInfo.SalesOrderID, orderInfo.OrderDate, orderInfo.TotalDue);
        }
        Console.WriteLine("");
    }
}

Example 3

The following example uses the SalesOrderHeader.Address and SalesOrderHeader.Contact navigation properties get the collection of Address and Contact objects associated with each order. The last name of the contact, the street address, the sales order number, and the total due for each order to the city of Seattle are returned in an anonymous type.

C# 
string city = "Seattle";
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    ObjectSet<SalesOrderHeader> orders = context.SalesOrderHeaders;

    var ordersQuery = from order in orders
                      where order.Address.City == city
                      select new
                      {
                          ContactLastName = order.Contact.LastName,
                          ContactFirstName = order.Contact.FirstName,
                          StreetAddress = order.Address.AddressLine1,
                          OrderNumber = order.SalesOrderNumber,
                          TotalDue = order.TotalDue
                      };

    foreach (var orderInfo in ordersQuery)
    {
        Console.WriteLine("Name: {0}, {1}", orderInfo.ContactLastName, orderInfo.ContactFirstName);
        Console.WriteLine($"Street address: {orderInfo.StreetAddress}");
        Console.WriteLine($"Order number: {orderInfo.OrderNumber}");
        Console.WriteLine($"Total Due: {orderInfo.TotalDue}");
        Console.WriteLine("");
    }
}

Example 4

The following example uses the Where method to find orders that were made after December 1, 2003, and then uses the order.SalesOrderDetail navigation property to get the details for each order.

C# 
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    IQueryable<SalesOrderHeader> query =
        from order in context.SalesOrderHeaders
        where order.OrderDate >= new DateTime(2003, 12, 1)
        select order;

    Console.WriteLine("Orders that were made after December 1, 2003:");
    foreach (SalesOrderHeader order in query)
    {
        Console.WriteLine($"OrderID {order.SalesOrderID} Order date: {order.OrderDate:d} ");
        foreach (SalesOrderDetail orderDetail in order.SalesOrderDetails)
        {
            Console.WriteLine($"  Product ID: {orderDetail.ProductID} Unit Price {orderDetail.UnitPrice}");
        }
    }
}

See also