Get distinct columns with order by date

I have these following two tables:

Job Title | PostDate | CompanyId
As开发者_如何学Gositant  | 12/15/10 | 10
Manager   | 12/1/10  | 11
Developer | 12/31/10 | 10
Assitant  | 12/1/10  | 13
PM        | 11/29/10 | 12

CompanyId | Name
10        | Google
11        | Yahoo
12        | Microsoft
13        | Oracle

Now i would like to get 3 different companies with the jobs sorted by post date. The result table would be following:

Job Title | PostDate | CompanyName
Developer | 12/31/10 | Google
Manager   | 12/1/10  | Yahoo
Assitant  | 12/1/10  | Oracle

How can I achieve that using a linq query? Any help will be appreciated...

I think that would be something like:

var query = from company in db.Companies
            join job in db.Jobs on company.CompanyId equals job.CompanyId
            group job by company into jobsByCompany
            let lastJob = jobsByCompany.OrderByDescending(x => x.PostDate)
                                       .First()
            orderby lastJob.PostDate descending
            select new
            {
                JobTitle = lastJob.JobTitle,
                PostDate = lastJob.PostDate,
                CompanyName = jobsByCompany.Key.Name
            };

It's a little odd to do a join and then a group - we could do a GroupJoin instead, but then discard empty options:

var query = from company in db.Companies
            join job in db.Jobs on company.CompanyId equals job.CompanyId
                 into jobsByCompany // Make this a group join
            let lastJob = jobsByCompany.OrderByDescending(x => x.PostDate)
                                       .FirstOrDefault()
            where lastJob != null
            orderby lastJob.PostDate descending
            select new
            {
                JobTitle = lastJob.JobTitle,
                PostDate = lastJob.PostDate,
                CompanyName = company.Name
            };

EDIT: Note that doesn't just take the top three results. Use query = query.Take(3); to just get the first three results.