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POHow to add a where clause on a linq join (lambda)?
 

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  1. POHow to add a where clause on a linq join (lambda)?
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    <p>I have two database tables Contact (Id, Name, ...) and ContactOperationalPlaces (ContactId, MunicipalityId), where a contact can be connected to several ContactOperationalPlaces.</p> <p>What I'm trying to do is to build a query (ASP .NET, C#) with IQueryable, that only selects all the contacts that exists in the ContactOperationalPlaces table, with a given MunicipalityId.</p> <p>The sql query looks like this:</p> <pre><code>select * from Contacts c right join ContactOperationPlaces cop on c.Id = cop.ContactId where cop.MunicipalityId = 301; </code></pre> <p>With linq it would look something like this:</p> <pre><code>//_ctx is the context var tmp = (from c in _ctx.Contacts join cop in _ctx.ContactOperationPlaces on c.Id equals cop.ContactId where cop.MunicipalityId == 301 select c); </code></pre> <p>So, I know how to do this if the point was to select all of this at once, unfortunately it's not. I'm building a query based on user input, so I don't know all of the selection at once.</p> <p>So this is what my code looks like:</p> <pre><code>IQueryable&lt;Contacts&gt; query = (from c in _ctx.Contacts select c); //Some other logic.... /*Gets a partial name (string nameStr), and filters the contacts so that only those with a match on names are selected*/ query = query.Where(c =&gt; c.Name.Contains(nameStr); //Some more logic //Gets the municipalityId and wants to filter on it! :( how to? query = query.where(c =&gt; c.ContactOperationalPlaces ...........?); </code></pre> <p>The difference with the two where statements is that with the first one, each contact has only one name, but with the latter a contact can contain several operational places...</p> <p>I have managed to find one solution, but this solution gives me an unidentyfied object, that contains both of the tables. And I don't know how to proceed with it.</p> <pre><code>query.Join(_ctx.ContactOperationPlaces, c =&gt; c.Id, cop =&gt; cop.ContactId, (c, cop) =&gt; new {c, cop}).Where(o =&gt; o.cop.municipalityId == 301); </code></pre> <p>The object returned from this expression is System.Linq.Iqueryable&lt;{c:Contact, cop:ContactOperationalPlace}>, and it can't be cast to Contacts...</p> <p>So, that's the issue. The answer is probably pretty simple, but I just can't find it...</p>
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