Silverlight 4:The method ‘Skip’ is only supported for sorted input in LINQ to Entities. The method ‘OrderBy’ must be called before the method ‘Skip’.

If you are using default domain service and Linq-to-Entities with silverlight 4, and you want to use data pager for your datagrid, you may end up with the error message above. In order to fix it, just open the corresponding get method for the entity and put .OrderBy("it.[ColumnName]");


[Query(IsDefault = true)]
public IQueryable GetRequests()
{
return this.ObjectContext.Requests.OrderBy("it.RequestID");
}

Binding foreignkeys and EF's entity by using EntityDataSource to Bindable Controls such as FormView, GridView

Here is a simple case. You have a Client table and a lkpClientType table and they have a referential relationship by lkpClientTypeID. And you want to show the ClientTypeID of the Client table in a data bindable control. How can you do it?

Here is a procedure to follow:

1. Create a EntityDataSource
2. Select Client as your source entity. (I assume that you know how to setup a edmx file.)
3. In VS 2008 designer, select the EDS and hit 'F4' to see a properties window.
4. Look for an include property field and type "lkpClientType"
5. Now in your bindable property value do something like <%#Bind("lkpClientType.ClientTypeID")%>

How to include a foreignkey in your own EF's entityobject?

If your EntityModel name is MyEntities and in your model, if you have Client class inherits from entityobject having a navigation or foreignkey relationship with lkpClientType class also inherits from entityobject, create a partial class like this.

   1:  Partial Public Class Client

   2:   

   3:      Public Property ClientTypeID() As Nullable(Of Integer)

   4:          Get

   5:              If lkpClientTypeReference Is Nothing Then

   6:                  Return Nothing

   7:              End If

   8:   

   9:              If lkpClientTypeReference.EntityKey Is Nothing Then

  10:                  Return Nothing

  11:              End If

  12:              Return lkpClientTypeReference.EntityKey.EntityKeyValues(0).Value

  13:          End Get

  14:   

  15:          Set(ByVal value As Nullable(Of Integer))

  16:              If value.HasValue Then

  17:                  ' To notify others listening that the property is changing

  18:                  OnPropertyChanging("ClientTypeID")

  19:                  lkpClientTypeReference.EntityKey = New EntityKey("MyEntities.lkpClientType", _

  20:                               New EntityKeyMember() {New EntityKeyMember("ClientTypeID", DirectCast(value.Value, Object))})

  21:                  OnPropertyChanged("ClientTypeID")

  22:              End If

  23:          End Set

  24:      End Property

  25:   

  26:  End Class

Once done creating the partial class and compiling, following query will include your foreignkey as well in your result set of Client:

Dim aClient= (from c in MyEntities.Client where c.ClientID = 1012 select c).First()
System.WriteLine(aClient.ClientTypeID)
Or
Var aClient= (from c in MyEntities.Client where c.ClientID = 1012 select c).First()
Sytem.WriteLine(aClient.ClientTypeID)