Dropdown list in photo album

sophia · April 14th, 2010, 03:34 AM

As in the book I am using the dropdown list in photo album (Default.aspx)

Code:

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" 
                DataSourceID="LinqDataSource1" DataTextField="Name" DataValueField="Id" 
                Width="129px">
                <asp:ListItem Value="">Please Choose Album</asp:ListItem>
            </asp:DropDownList>

And LinqDataSource1 is defines as follows

Code:

<asp:LinqDataSource ID="LinqDataSource1" runat="server" ContextTypeName="JackGenieDataContext" Select="new (Id, Name)" 
                    TableName="PhotoAlbums">
                </asp:LinqDataSource>

But when I see it in browser then it does not show this option and directly fills it up with the available albums and shows the first album in list (sonic youth for instance).
Where does go the Please Choose Album. have I made some mistake?
thank you.

Imar · April 14th, 2010, 03:43 AM

The book doesn't haven't a "Please choose an album" option, does it? So I am not sure what exactly you're asking....

Imar

sophia · April 14th, 2010, 03:59 AM

I am saying that as you have a dropdown list in Reviews.aspx to filter the reviews based on specific genre but also have an option something like "Please choose Genre", likewise I am trying to add such option "Please choose Photo Album" in Default.aspx for Photo albums. But here you use the Linqdata Source so I am not getting that option "Please choose Photo Album" in the browser.

Hence I just wanna ask that how I can add such option in case of LinqData Source.
Thank you.

Imar · April 14th, 2010, 04:09 AM

Ah, that helps. being specific makes it easier for me to help you.

AppendDataBoundItems="True" is the key.....

Imar

sophia · April 14th, 2010, 04:20 AM

Hello, as soon as I added the AppendDataBoundItems then an error was generated.

Code:

Operator '==' incompatible with operand types 'Int32' and 'Object'

Dropdown list is as follows

Code:

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" AppendDataBoundItems="true" 
                DataSourceID="LinqDataSource1" DataTextField="Name" DataValueField="Id" 
                Width="129px">
                <asp:ListItem Value="">Please Choose Album</asp:ListItem>
            </asp:DropDownList>

And Data source is as follows.

Code:

<asp:LinqDataSource ID="LinqDataSource1" runat="server" ContextTypeName="SiteDataContext" Select="new (Id, Name)" 
                    TableName="PhotoAlbums">
                </asp:LinqDataSource>

I am using same table structure as in the book.
What has gone wrong now? As it was not giving any error without AppendDataBoundItems.

Imar · April 14th, 2010, 11:19 AM

You could set a default value of an ID that doesn't exist in the database, like -1, to the Value of the ListItem. Cheesy, but t works...

Imar

sophia · April 14th, 2010, 02:40 PM

hello,
I did set the value to -1 but it got me other error.

I used the code as follows

Code:

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" AppendDataBoundItems="true"  
                DataSourceID="LinqDataSource1" DataTextField="Name" DataValueField="Id" 
                Width="129px">
                <asp:ListItem Value="-1">Please Choose Album</asp:ListItem>
            </asp:DropDownList>

And the error was

Code:

Sequence contains no elements

Line 21:         Using myDatabaseContext As JackGenieDataContext = New JackGenieDataContext()
Line 22: 
Line 23:             Dim photoAlbumOwner As String = (From p In myDatabaseContext.PhotoAlbums _
Line 24:               Where p.Id = photoAlbumId _
Line 25:               Select p.UserName).Single()

Imar · April 14th, 2010, 03:14 PM

Try SingleOrDefault instead of just Single. When there's no matching record, SingleOrDefault will return null / Nothing. You can check for that value, and skip remaining code when the item is null.

Cheers,

Imar

sophia · April 14th, 2010, 03:24 PM

Thanks working now.
but also shows the EmptyDataTemplate (that is, album does not has any photos in it) with "Please Choose Album" option which is set for list view

Code:

 <EmptyDataTemplate>
                    Sorry,Album Has No Any Photos In It.
                </EmptyDataTemplate>

It does not make sense to see this message with Please Choose Album.

Imar · April 14th, 2010, 03:29 PM

You can set the Visible property of the list control to False if the item is Nothing...

Imar