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POLazy-Loading with two navigation properties
 

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  1. POLazy-Loading with two navigation properties
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    <h2>The Setup</h2> <p>I have a fairly simple 3 class set up as follows. There are a bunch of other properties of course, but they are not relevant here.</p> <p><strong>Models</strong></p> <pre><code>public class Employee { public int EmployeeId { get; set; } public string UserName { get; set; } public string Name { get; set; } public ICollection&lt;Position&gt; Positions { get; set; } } public class Position { public int PositionId { get; set; } public int EmployeeId { get; set; } [ForeignKey("EmployeeId")] public Employee Employee { get; set; } public int location { get; set; } [ForeignKey("location")] public Location Location { get; set; } } public class Location { public int LocationId { get; set; } public string Name { get; set; } } </code></pre> <p><strong>Controller</strong></p> <pre><code>public ActionResult Index() { string username = User.Identity.Name; Employee emp = context.Employees.Include(e =&gt; e.Positions).FirstOrDefault(e =&gt; e.UserName == username); return View(emp); </code></pre> <p><strong>View</strong></p> <pre><code>@model Employee &lt;h1&gt;Hi @Model.Name&lt;/h1&gt; &lt;ul&gt; @foreach (var position in @Model.Positions) { &lt;li&gt;@position.Name - @position.Location.Name&lt;/li&gt; } &lt;/ul&gt; </code></pre> <h2>The Problem</h2> <p>Now the problem is that because of Lazy Loading. I get a <em>NullReferenceException</em> on the <code>@item.Location.Name</code> call. It is loading the Position just fine (the item in the foreach).</p> <p>I have tried changing my Include to be:</p> <pre><code>context.Employees.Include("Positions.Location").FirstOrDefault(e =&gt; e.UserName == username); </code></pre> <p>But then I get the error: <em>More than one item in the metadata collection match the identity 'Location'.</em></p> <p>If I change the <code>Location</code> property on <code>Position</code> to <code>PositionLocation</code> then I get: <em>System.Reflection.AmbiguousMatchException: Ambiguous match found.</em></p> <p>Should I be using a ViewModel that I load with multiple queries to my context in my controller? That seems like a lot more code to maintain and I'd rather not if I don't have to.</p>
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    1. USMichael Dunlap
    1. USMichael Dunlap
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    1. COI wonder if there is an issue with the fact that you are calling your Location class the same name as a property used in the Position class.
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      1. UScorylulu
    2. CO@Corylulu Tried changing the Property to "PositionLocation" and now I get `System.Reflection.AmbiguousMatchException: Ambiguous match found.`
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      1. USMichael Dunlap
    3. COAre you sure you made all the changes correctly? You updated all instances of where you reference Location accordingly? It seems like something got left out. Perhaps edit the entire code to reflect any new changes.
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      1. UScorylulu
 

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