ASP.NET 2.0 Databinding help with an implementation

Posted By: Winston Pang | Apr 16th, 2007 @ 3:47 PM
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#Apr 16th, 2007 @ 3:47 PM
Winston Pang
Winston Pang

So i'm making my own Blog, and it's going to be simple the general layout is:


DATE - POST TITLE
- - - - - - - - - - - - - - - - -
POST CONTENTS
- - - - - - - - - - - - - - - - -
TAGS | COMMENT LINK(NUMBER OF COMMENTS)


So i've used a GridView, and supplied an SqlDataSource all works well, but now i'm trying to incorporate the TAGS feature, but it's kind of hard to do it all in the one single query, i don't think it's even possible.


My current schema goes something like this


Post - PostID_PK, Post title, etc
Comment - CommentID_PK, CommentContents, PostID_FK
Tag - TagID_PK, TagName
Tag_Post - Tag_Post_ID_PK, TagID_FK, PostID_FK

So that's the general layout, for my SqlDataSource i've got a query that will fetch all Posts, and also fetch the number of comments for each post, just a count. Works all well. But now i need to fetch all the Post_Tag records for EACH post, the results will be strange and i'm not sure how it'll work out in DataBinding.

My next step is to make my own custom data source objects, but i'm not exactly sure how i should model my custom data source objects for me to make my <%# Eval("FieldName") %> calls work still inside my aspx page.

Thank you in advance.


Winston

#Apr 16th, 2007 @ 4:36 PM
odujosh
odujosh
Need Microsoft SUX now!
ObjectDataSource.

Make  Class that does multiple queries or calls a Data Access Layer that does. Bind an instance of class to your gridview via a Object DataSource.
#Apr 16th, 2007 @ 5:08 PM
Winston Pang
Winston Pang

Thanks i'll look into that.

What i don't understand is, Using the ObjectDataSource, and if it's a Select method that i create, what type of object is the ObjectDataSource expecting, i'm assuming it should be a List, so that when Binding occurs, it traverses the lists and instantiates a new ItemTemplate for each record in the List, am i on the right track?

Furthermore if i have custom object types inside the list, does that mean when i do Eval calls, i specify the Property name as the string inside the Eval arguments?

Furthermore i think the logic behind doing all the mutliple calls will still be complicated.

As firstly, i'd be selecting all the Posts from the table. So i'll end up with a set of Post records, i'd then have to traverse this set of records and get the Post ID one by one and apply each ID into a select statement to select all the Tags that associated with that Post ID, it might be really inefficient, i'm not sure how i would also mangle the results of the Post record with a list of tags.

I must be doing something wrong here.

Any other pointers from anyone else?


Thank you once again.

#Apr 17th, 2007 @ 8:22 AM
odujosh
odujosh
Need Microsoft SUX now!
ObjectDataSource uses generics with collections. You make a class that represents the idea of data you input into it like:


public class Person
{

/*use properties if you care about that sort of thing I omit them for
conciseness */

public string FirstName;
public string LastName;
public DateTime BirthDate;
public List<Person> Babies;
}

Then you can bind using standard <%# %> statements using Eval and standard C# calls.

You Data Access Layer would then just bind data to List<Persons> or any collection that implemenets IEnumerable<T>
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