Question

I use EF 4 and C#.

I have a query like:

var contentsAuthor = from c in context.CmsContents
                     join a in context.CmsAuthors on c.AuthorId equals a.AuthorId
                     where a.UserId == userGuid
                     select new
                     {
                         c.Title,
                         c.ContentId
                     };

I would like rewrite it in Linq with Lambda Expression.
My questions:

• How to rewrite it?
• What is the appropriate name for my query syntax and the new with Linq and Lambda (query expression and Linq to Entities???). Please give me a hit on this point I’m confused.

Notes: probably the title for this question is not appropriate, let me know I will improve it

Thanks guys for your help on this!

Answer 1

The lambda expression should look like:

var contentsAuthor = context.CmsContents
                            .Join(context.CmsAuthors, 
                                  content => content.AuthorId,
                                  author => author.AuthorId,
                                  (content,  author) => new { content, author })
                            .Where(x => x.author.UserId == userGuid)
                            .Select(x => new { x.content.Title, x.content.ContentId });

Both yours and this version are LINQ queries. This one uses lambdas directly whereas your version uses syntactic sugar available in C#. They are the same. LINQ-to-Entities have nothing to do with this.

Anyway if you are using LINQ-to-Entities your CmsContent should have Author property and your query would reduce to:

var contentsAuthor = context.CmsContents
                            .Where(c => c.Author.UserId == userGuid)
                            .Select(c => new { c.Title, c.ContentId });

The LINQ-to-Entities provider will make join for you when translating expression tree to SQL query.