How to: Navigate Relationships Using Navigation Properties

This topic shows how to navigate relationships through navigation properties. For more information, see Navigation Properties. The 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 same example is shown using each of the following Entity Framework query technologies:

• LINQ to Entities

• Entity SQL with ObjectQuery<T>

• Query builder methods of ObjectQuery<T>

The example in this topic is based on the Adventure Works Sales Model. To run the code in this topic, you must have already added the Adventure Works Sales Model to your project and configured your project to use the Entity Framework. For more information, see How to: Use the Entity Data Model Wizard (Entity Framework) or How to: Manually Configure an Entity Framework Project and How to: Manually Define an Entity Data Model (Entity Framework).

Example

This is the LINQ to Entities example.

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

    Dim ordersQuery = From contact In contacts _
        Where contact.LastName = lastName _
        Select New With _
                {.LastName = contact.LastName, _
                 .Orders = contact.SalesOrderHeaders}

    For Each order In ordersQuery
        Console.WriteLine("Name: {0}", order.LastName)
        For Each orderInfo In order.Orders

            Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}", _
                    orderInfo.SalesOrderID, orderInfo.OrderDate, orderInfo.TotalDue)
        Next

        Console.WriteLine("")
    Next
End Using

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: {0}", 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("");
    }
}

This is the Entity SQL example.

Using context As New AdventureWorksEntities()
    Dim esqlQuery As String = "SELECT c.FirstName, c.SalesOrderHeaders " & _
        " FROM AdventureWorksEntities.Contacts AS c where c.LastName = @ln"

    Dim query As New ObjectQuery(Of DbDataRecord)(esqlQuery, context)

    ' Add parameters to the collection. 
    query.Parameters.Add(New ObjectParameter("ln", "Zhou"))

    For Each rec As DbDataRecord In query

        ' Display contact's first name. 
        Console.WriteLine("First Name {0}: ", rec(0))
        Dim list As List(Of SalesOrderHeader) = TryCast(rec(1), List(Of SalesOrderHeader))
        ' Display SalesOrderHeader information 
        ' associated with the contact. 
        For Each soh As SalesOrderHeader In list
            Console.WriteLine(" Order ID: {0}, Order date: {1}, Total Due: {2}",
                              soh.SalesOrderID, soh.OrderDate, soh.TotalDue)
        Next
    Next
End Using

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    string esqlQuery = @"SELECT c.FirstName, c.SalesOrderHeaders 
        FROM AdventureWorksEntities.Contacts AS c where c.LastName = @ln";
    ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(esqlQuery, context);
    query.Parameters.Add(new ObjectParameter("ln", "Zhou"));

    foreach (DbDataRecord rec in query)
    {

        // Display contact's first name.
        Console.WriteLine("First Name {0}: ", rec[0]);
        List<SalesOrderHeader> list = rec[1] as List<SalesOrderHeader>;
        // Display SalesOrderHeader information 
        // associated with the contact.
        foreach (SalesOrderHeader soh in list)
        {
            Console.WriteLine("   Order ID: {0}, Order date: {1}, Total Due: {2}",
                soh.SalesOrderID, soh.OrderDate, soh.TotalDue);
        }
    }
}

This is the query builder method example.

Dim lastName = "Zhou"

Using context As New AdventureWorksEntities()
    ' Define a query that returns a nested 
    ' DbDataRecord for the projection. 
    Dim query As ObjectQuery(Of DbDataRecord) = context.Contacts.Select("it.FirstName, it.LastName, it.SalesOrderHeaders") _
                                                .Where("it.LastName = @ln", New ObjectParameter("ln", lastName))

    For Each rec As DbDataRecord In query.Execute(MergeOption.AppendOnly)

        ' Display contact's first name. 
        Console.WriteLine("First Name {0}: ", rec(0))
        Dim list As List(Of SalesOrderHeader) = TryCast(rec(2), List(Of SalesOrderHeader))
        ' Display SalesOrderHeader information 
        ' associated with the contact. 
        For Each soh As SalesOrderHeader In list
            Console.WriteLine(" Order ID: {0}, Order date: {1}, Total Due: {2}", _
                              soh.SalesOrderID, soh.OrderDate, soh.TotalDue)
        Next
    Next
End Using

string lastName = "Zhou";
using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    // Define a query that returns a nested 
    // DbDataRecord for the projection.
    ObjectQuery<DbDataRecord> query =
        context.Contacts.Select("it.FirstName, "
            + "it.LastName, it.SalesOrderHeaders")
        .Where("it.LastName = @ln", new ObjectParameter("ln", lastName));

    foreach (DbDataRecord rec in
        query.Execute(MergeOption.AppendOnly))
    {

        // Display contact's first name.
        Console.WriteLine("First Name {0}: ", rec[0]);
        List<SalesOrderHeader> list = rec[2]
            as List<SalesOrderHeader>;
        // Display SalesOrderHeader information 
        // associated with the contact.
        foreach (SalesOrderHeader soh in list)
        {
            Console.WriteLine("   Order ID: {0}, " +
                "Order date: {1}, Total Due: {2}",
                soh.SalesOrderID, soh.OrderDate, soh.TotalDue);
        }
    }
}

See Also

Tasks

How to: Use Query Paths to Shape Results

Concepts

Querying a Conceptual Model
Defining and Managing Relationships