ch 14: AllByGenre.aspx.cs

binaryspirit · May 4th, 2012, 04:21 AM

using (PlanetHarmonyEntities myEntities = new PlanetHarmonyEntities())
{
var allGenres = from genre in myEntities.Genres
orderby genre.Name
select new { genre.Name, genre.Reviews };
Repeater1.DataSource = allGenres;
Repeater1.DataBind();
}
I don't understand how the title of the reviews are fetched using genre object
plz help.

Imar · May 4th, 2012, 04:52 AM

Hi there,

A Genre and a Review have a relationship in the database. Just as a Review a Genre, so has a Genre a collection of associated Reviews. This means that

myGenre.Reviews

would give you all the reviews that belong to that genre. And this is what the LINQ query does:

Code:

select new { genre.Name, genre.Reviews };

It selects a new anonymous object with two properties: a Name of the genre and a collection of all associated reviews. This means you can then loop over the result set and display all genre names. Within that loop, you can loop over all reviews for that genre and display their info, including the title.

Check out page 495 and further for a detailed explanation including a class diagram of the anonymous type as well as a diagram that shows the relationship between the genre's Name and the collection of reviews.

Hope this helps,

Imar

binaryspirit · May 4th, 2012, 05:09 AM

thanx for the quick reply sir,
still i dont get it fully, does it internally creating join between the tables?

Imar · May 4th, 2012, 05:19 AM

You created a relationship between the two tables. When you then create an Entity Framework on top of the database, code gets generated that links a Genre instance to a Review instance. Without the proper relationship between those tables, the two objects won't be related in your EF model either.

When the query then gets executed (remember, LINQ queries for EF are translated to SQL), EF indeed creates a query that joins these two tables.

Cheers,

Imar

binaryspirit · May 4th, 2012, 08:38 AM

for some reason, after navigating to ManagePhotoAlbum.aspx i m able to insert the required values in the textbox, and its updated in the picture table, but not showing in the page, neither the delete button etc.

(sorry for not posting it in separate thread)

Code: ManagePhotoAlbum.aspx
<%@ Page Title="Manage Photo Album" Language="C#" MasterPageFile="~/MasterPages/Frontend.master" AutoEventWireup="true" CodeFile="ManagePhotoAlbum.aspx.cs" Inherits="ManagePhotoAlbum" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="cpMainContent" Runat="Server">
<asp:ListView ID="ListView1" runat="server" DataKeyNames="Id"
DataSourceID="EntityDataSource1" InsertItemPosition="LastItem">

<InsertItemTemplate>
<li style="">
Description:
<asp:TextBox ID="DescriptionTextBox" runat="server"
Text='<%# Bind("Description") %>' />
 ToolTip:
<asp:TextBox ID="ToolTipTextBox" runat="server" Text='<%# Bind("ToolTip") %>' />
 ImageUrl:
<asp:TextBox ID="ImageUrlTextBox" runat="server"
Text='<%# Bind("ImageUrl") %>' />
 
<asp:Button ID="InsertButton" runat="server" CommandName="Insert"
Text="Insert" />
<asp:Button ID="CancelButton" runat="server" CommandName="Cancel"
Text="Clear" />
</li>
</InsertItemTemplate>

<ItemTemplate>
<li style="">
Description:
<asp:Label ID="DescriptionLabel" runat="server"
Text='<%# Eval("Description") %>' />
 
ToolTip:
<asp:Label ID="ToolTipLabel" runat="server" Text='<%# Eval("ToolTip") %>' />
 
ImageUrl:
<asp:Label ID="ImageUrlLabel" runat="server" Text='<%# Eval("ImageUrl") %>' />
 
<asp:Button ID="DeleteButton" runat="server" CommandName="Delete"
Text="Delete" />
</li>
</ItemTemplate>
<LayoutTemplate>
<ul class="ItemContainer">
<li runat="server" id="itemPlaceholder" />
</ul>
</LayoutTemplate>

</asp:ListView>
<asp:EntityDataSource ID="EntityDataSource1" runat="server"
ConnectionString="name=PlanetHarmonyEntities"
DefaultContainerName="PlanetHarmonyEntities" EnableDelete="True"
EnableFlattening="False" EnableInsert="True" EntitySetName="Pictures"
Where="it.PhotoAlbum.Id= @PhotoAlbumId"
oninserting="EntityDataSource1_Inserting">
<WhereParameters>
<asp:QueryStringParameter Name="PhotoAlbumId" QueryStringField="Id"
Type="Int32" />
</WhereParameters>
</asp:EntityDataSource>
</asp:Content>

Imar · May 4th, 2012, 08:50 AM

Quote:

(sorry for not posting it in separate thread)

Then why didn't you create a separate thread? Makes stuff easier to find and manage.

Anyway, I think the problem is in the parameter setup:

Code:

 
<asp:QueryStringParameter Name="photoAlbumId" QueryStringField="Id" Type="Int32" />

Notice how your code use Id as the query string field. The NewPhotoAlbum.aspx page passes PhotoAlbumId to this page instead. Change Id ito PhotoAlbumId and I think it should work.

Cheers,

Imar

binaryspirit · May 4th, 2012, 09:08 AM

oh yes hvnt recognized it, many thanx to u.