Yes you can.
First, create a Repository class. Put it in the DAL folder. The repository constructor will instantiate an object(context) of the Entity model you have. It will contain all the methods you use to retrieve, save and update data.
Next, create a BLL folder and place all your extended partial classes and all other classes you created that will be used to decide which data to return to the content page based on passed in parameters. These methods will instantiate an object of the repository and the call the repository methods. If a class accesses the repository and then does anything with the data like parse, filter, send in parameters, it should be in the BLL.
Third, On your content pages, use the ObjectDataSource control to attach the select, update, delete methods to the BLL classes and methods. The topic is large and not for beginners, but learn it and do it! It will be well worth it.
Example of the ObjectDataSource control markup in content page:
<asp:objectdatasource id="ImagesObjectDataSource" runat="server" typename="BLL.ImageData" xmlns:asp="#unknown">
DataObjectTypeName="BLL.ImageData" SelectMethod="GetAllPhotos" DeleteMethod="DeleteImage"
UpdateMethod="UpdateImage" OnUpdated="ImagesObjectDataSource_Updated" OldValuesParameterFormatString="orig{0}"
OnUpdating="MappImagesObjectDataSource_Updating" OnDeleted="ImagesObjectDataSource_Deleted"
ConflictDetection="CompareAllValues">
<SelectParameters>
<asp:querystringparameter name="imageID" querystringfield="imageID" type="String" />
</SelectParameters>
<updateparameters>
<asp:parameter name="ImageData" type="Object" />
<asp:parameter name="origImageData" type="Object" />
</updateparameters>
</asp:objectdatasource>
As you can see from the ObjectDataSources' DataObjectTypeName and TypeName properties that they are connected to the BLL.ImageData class. The BLL.ImageData class has methods to get and process the data returned from calling repository methods.
That is ASP.Net web site N-Tier in a nut shell. Of course there are many implementations. But your logical layers are there.
Search for using the ObjectDataSource control for more information.