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POHow to do multiple joins when using groupby in linq
 

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  1. POHow to do multiple joins when using groupby in linq
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    <p>I have a picturerating table in my database. For every new rating ,a new picture rating table row will be created. I am grouping those ratings by lastweek and pictureid, meaning all the ratings for one single pic in the last week will be accumulated and become one rating.Then i will be able to sort them by thier count.</p> <p>This is my picturerating table :</p> <pre><code>public partial class picturerating { public int idpicturerating { get; set; } public int idpictures { get; set; } public int iduser { get; set; } public System.DateTime iddatetime { get; set; } public int iduserratedby { get; set; } public int rating { get; set; } } </code></pre> <p>This is my code to do this :</p> <pre><code> public IQueryable&lt;SortedDto&gt; GetRatignsAndTheirDetails() { var pastDate = DateTime.Now.Date.AddDays(-7); var combo = from p in db.picturerating where p.iddatetime &gt; pastDate group p by p.idpictures into pgroup let count = pgroup.Count() orderby count descending select new SortedDto { IdPictures = pgroup.FirstOrDefault().idpictures, IdPicturerating = pgroup.FirstOrDefault().idpicturerating, IdUser = pgroup.FirstOrDefault().iduser, IdDatetime = pgroup.FirstOrDefault().iddatetime, IdUserratedBy = pgroup.FirstOrDefault().iduserratedby, }; return combo; } </code></pre> <p>Now here comes my problem:</p> <p>How to join two more tables , users and picturedetails table to show username and total rating.</p> <p>As per now i am able to write this code, this is just a rough idea in my mind not a proper code so i need help to change this code to make it work:</p> <pre><code> var pastDate = DateTime.Now.Date.AddDays(-1); var combo = from p in db.picturedetails join u in db.users on p.iduser equals u.iduser join l in db.pictureratings where l.iddatetime &gt; pastDate group l by l.idpictures into pgroup let count = pgroup.Count() orderby count descending select new SortedDto { IdPictures = pgroup.FirstOrDefault().idpictures, IdPictureRating = pgroup.FirstOrDefault().idpicturerating, IdUser = pgroup.FirstOrDefault().iduser, IdDatetime = pgroup.FirstOrDefault().iddatetime, IdUserRatedBy = pgroup.FirstOrDefault().iduserrateddby, username=u.username, dob=u.dob, sex=u.sex, totalrating = pl.Average(l =&gt; (float?)l.rating)?? 0 , // pl.Where(a =&gt; a.ratenumber!= null).Average(c =&gt; c.ratenumber) }; return combo; </code></pre> <p>Am i doing it right, whats the way to do it, how to change the above code to make it work properly as per my needs. </p>
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    1. PTQuestion
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    1. USObvious
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    1. COSo what does not work properly?
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      1. POHow to do multiple joins when using groupby in linq
      1. USGert Arnold
    2. COThe joins in the third code, i have written them just to give you an idea, is it the way i should join?
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      1. USObvious
 

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