linq to sql -> join - sql

Question

SQL query:
SELECT ArticleCategories.Title AS Category, Articles.Title, Articles.[Content], Articles.Date
FROM ArticleCategories INNER JOIN
Articles ON ArticleCategories.CategoryID = Articles.CategoryID
Object repository:
public class ArticleDisplay
{
public int CategoryID;
public string CategoryTitle;
public int ArticleID;
public string ArticleTitle;
//public string ArticleDate;
public string ArticleContent;
}
public class ArticleRepository
{
private DB db = new DB();
//
// Query Methods
public IQueryable<ArticleDisplay> FindAllArticles()
{
var result = from category in db.ArticleCategories
join article in db.Articles on category.CategoryID equals article.CategoryID
select new
{
CategoryID = category.CategoryID,
CategoryTitle = category.Title,
ArticleID = article.ArticleID,
ArticleTitle = article.Title,
//ArticleDate = article.Date,
ArticleContent = article.Content
};
return result;
}
....
}
And finally, I get this error:
Error 1 Cannot implicitly convert type
'System.Linq.IQueryable'
to
'System.Linq.IQueryable'.
An explicit conversion exists (are you
missing a cast?) C:\Documents and
Settings\ilija\My Documents\Visual
Studio
2008\Projects\CMS\CMS\Models\ArticleRepository.cs 29 20 CMS
Any idea what did I do wrong?
Thanks,
Ile

Answer 1

Your method has a return type of IQueryable<Article>, but your LINQ query is not returning articles. Instead it's trying to return an anonymous type made up of properties from both category and article. You could create a class to hold this combination of properties and change the method signature to use that class.

Answer 2

As Adam said, if you're not wanting to return the full article class then you'll need to return your own class.
public IQueryable<ArticleDisplay> FindAllArticles()
{
var result = from category in db.ArticleCategories
join article in db.Articles on category.CategoryID equals article.CategoryID
select new ArticleDisplay() //specify your new class
{
CategoryID = category.CategoryID,
CategoryTitle = category.Title,
....
};
return result;
}
Your updated code still returns an anonymous class....