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PONHibernate.Linq, WCF RIA Services, weird error
 

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    <p>I have a Silverlight Business Application project set up, with these codes.</p> <p>I have this domain class:</p> <pre><code>public class BaseDomain { public virtual Guid Id { get; set; } public virtual DateTime CreatedOn { get; set; } } public class Sector : BaseDomain { public virtual string Code { get; set; } public virtual string Name { get; set; } } </code></pre> <p>The domain objects mapping has been set up and working fine.</p> <p>The I have this DTO class:</p> <pre><code>public class SectorDto : BaseDto { [Key] public virtual Guid Id { get; set; } public virtual DateTime CreatedOn { get; set; } public virtual string Code { get; set; } public virtual string Name { get; set; } public SectorDto() { } public SectorDto(Sector d) { Id = d.Id; CreatedOn = d.CreatedOn; Code = d.Code; Name = d.Name; } } </code></pre> <p>DTO is used to flatten the object and make sure no unnecessary relations from being serialized and transfered over the wire.</p> <p>Then I have this RIA DomainService (there are several variations of the GetSectors() method, I'll explain later):</p> <pre><code>[EnableClientAccess] public class OrganizationService : BaseDomainService { public IQueryable&lt;SectorDto&gt; GetSectors1() { return GetSession().Linq&lt;Sector&gt;() .Select(x =&gt; Mapper.Map&lt;Sector, SectorDto&gt;(x)); } public IQueryable&lt;SectorDto&gt; GetSectors2() { return GetSession().Linq&lt;Sector&gt;().ToList() .Select(x =&gt; new SectorDto(x)).AsQueryable(); } public IQueryable&lt;SectorDto&gt; GetSectors3() { return GetSession().Linq&lt;Sector&gt;().Select(x =&gt; new SectorDto(x)); } public IQueryable&lt;SectorDto&gt; GetSectors4() { return GetSession().Linq&lt;Sector&gt;().Select(x =&gt; new SectorDto() { Id = x.Id, CreatedOn = x.CreatedOn, Name = x.Name, Code = x.Code }); } } </code></pre> <p>BaseDomainService is just a parent class that provides handling for NHibernate session. I set the session to live per web request.</p> <p>Then I hook up the service to a DataGrid (Silverlight Toolkit) in a XAML page:</p> <pre><code>var ctx = new App.Web.Services.OrganizationContext(); SectorGrid.ItemsSource = ctx.SectorDtos; ctx.Load(s.GetSectors1Query()); </code></pre> <p>When calling the various methods, I got these results:</p> <ol> <li><p>Method <strong>GetSectors1()</strong> produce an exception <em>"Load operation failed for query 'GetSectors1'. Unable to cast object of type NHibernate.Linq.Expressions.EntityExpression' to type 'NHibernate.Linq.Expressions.CollectionAccessExpression'."</em>. </p> <p>This is the best way that I'm trying to achive. I want to use the <a href="http://automapper.codeplex.com/" rel="nofollow noreferrer">AutoMapper</a> library to automatically map the domain class to the DTO. I'm quite positive that the problem is not from the AutoMapper since I also get the error if I call a method from inside the anonymous method passed into Select, eg. <code>GetSession().Linq&lt;Sector&gt;().Select(x =&gt; CustomMap(x))</code>.</p></li> <li><p>Method <strong>GetSectors2()</strong> displays the data correctly in the grid, but this defeats the purpose of using IQueryable, the call would not be lazy evaluated.</p></li> <li><p>Method <strong>GetSectors3()</strong> fetches the data, but only the Id and CreatedOn which is in the parent class BaseDomain. The Code and Name are both null.</p></li> <li><p>Method <strong>GetSectors4()</strong> fetches the data correctly and lazily evaluated, but I don't want to manually map my domain to DTO every time like this!</p></li> </ol> <p>So what gives? The results are so far away than what I expected! Any idea on how to make this work? Any advice? </p> <p>I appreciate any help, I'm nearly lost. Thank you very much.</p>
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    1. COHave you tried using HQL or the Criteria API instead of Linq? Does it work then?
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    2. COI need LINQ to get the result as IQueryable, so that RIA Service DomainDataSource control can automatically handle paging, filtering, sorting, etc.
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    3. COHave you tried the Linq provider in the NHibernate trunk (versus the NHContrib Linq provider you appear to be using now)?
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      1. USMichael Maddox
 

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