EntityQuery Class

Article
01/27/2012

[WCF RIA Services Version 1 Service Pack 2 is compatible with either .NET framework 4 or .NET Framework 4.5, and with either Silverlight 4 or Silverlight 5.]

Represents a query method invocation.

Inheritance Hierarchy

System.Object
System.ServiceModel.DomainServices.Client.EntityQuery
System.ServiceModel.DomainServices.Client.EntityQuery<TEntity>

Namespace: System.ServiceModel.DomainServices.Client
Assembly: System.ServiceModel.DomainServices.Client (in System.ServiceModel.DomainServices.Client.dll)

Syntax

'Declaration
Public MustInherit Class EntityQuery

'Usage
Dim instance As EntityQuery

public abstract class EntityQuery

public ref class EntityQuery abstract

[<AbstractClassAttribute>]
type EntityQuery =  class end

public abstract class EntityQuery

The EntityQuery type exposes the following members.

Properties

	Name	Description
	DomainClient	Gets the DomainClient for this query.
	EntityType	Gets the type this query retrieves data from.
	HasSideEffects	Gets a value indicating whether the query has side-effects.
	IncludeTotalCount	Gets or sets a value indicating whether the TotalEntityCount property is required.
	IsComposable	Gets a value indicating if the query supports composition.
	Parameters	Gets the parameters required by the query method.
	Query	Gets the underlying IQueryable for the query.
	QueryName	Gets the name of the query method.

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Methods

	Name	Description
	Equals	(Inherited from Object.)
	Finalize	(Inherited from Object.)
	GetHashCode	(Inherited from Object.)
	GetType	(Inherited from Object.)
	MemberwiseClone	(Inherited from Object.)
	ToString	(Inherited from Object.)

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Remarks

In your client application, you can apply additional filtering on a query to limit which entities are returned. You use LINQ and a subset of LINQ query operators to modify the results returned from the query. The following lists the available query operators:

Where
OrderBy
ThenBy
Skip
Take

After you apply additional filtering, you pass the EntityQuery object as a parameter in the Load method to execute the query and get the results. If the query has a QueryAttribute with the IsComposable property set to false, you cannot apply additional filtering on the query. Generally, only queries that return a single entity will have IsComposable set to false.

Examples

The following code shows how to retrieve customers from the domain service. It filters customers who have phone numbers that start with 583 and orders them alphabetically by LastName. The results are displayed in a DataGrid.

Partial Public Class MainPage
    Inherits UserControl

    Private _customerContext As New CustomerDomainContext

    Public Sub New()
        InitializeComponent()

        Dim query As EntityQuery(Of Customer)

        query = _
            From c In Me._customerContext.GetCustomersQuery() _
            Where c.Phone.StartsWith("583") _
            Order By c.LastName

        Dim loadOp = Me._customerContext.Load(query)
        CustomerGrid.ItemsSource = loadOp.Entities
    End Sub

End Class

public partial class MainPage : UserControl
{
    private CustomerDomainContext _customerContext = new CustomerDomainContext();

    public MainPage()
    {
        InitializeComponent();
        EntityQuery<Customer> query = 
            from c in _customerContext.GetCustomersQuery()
            where c.Phone.StartsWith("583")
            orderby c.LastName
            select c;
        LoadOperation<Customer> loadOp = this._customerContext.Load(query);
        CustomerGrid.ItemsSource = loadOp.Entities;
    }
}

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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