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    <p>Yes, the different behaviour is normal and it occurs because of <em>Relationship Fixup</em>.</p> <p>When you load only one <code>SiteMember</code> with <code>FirstOrDefault</code> the two collections <code>InvitationsSent</code> and <code>InvitationsReceived</code> will be loaded as well as soon as you access them (or inspect them in the debugger) because they are marked as <code>virtual</code> and lazy loading will apply. But the <code>FriendshipInvitation</code>s in those collections won't lazily load the <code>InvitingUser</code> or the <code>InvitedUser</code> because these navigation properties are <em>not</em> marked as <code>virtual</code>.</p> <p>Say, <code>SiteMember</code> 1 that you load with <code>FirstOrDefault</code> has an invitation received from <code>SiteMember</code> 2 and no invitation sent. So, <code>InvitationsReceived</code> will contain one element and <code>InvitationsSent</code> will be empty. That element - a <code>FriendshipInvitation</code> entity - will have <code>InvitingUser</code> as 2 and <code>InvitedUser</code> as 1. The <code>InvitingUser</code> will be <code>null</code> in that case because it can't be lazily loaded (since it isn't <code>virtual</code>) and the <code>SiteMember</code> 2 isn't loaded yet into the context. (<code>InvitedUser</code> however will be a dynamic proxy to <code>SiteMember</code> 1 because you already have loaded the <code>SiteMember</code> 1, see next paragraph.)</p> <p>However, if you load <em>all</em> <code>SiteMember</code>s with <code>ToList()</code> the <code>SiteMember</code> 2 will be loaded as well into the context with the query executed by <code>ToList()</code>. EF will set the <code>InvitingUser</code> 2 automatically to the already loaded entity which is called <em>Relationship Fixup</em>. It is <em>not</em> loaded by lazy loading of the <code>InvitingUser</code> navigation property because lazy loading isn't supported for a not <code>virtual</code> property.</p> <p>To have a consistent behaviour and not rely on Relationship Fixup alone I would suggest that you mark the <code>InvitingUser</code> and <code>InvitedUser</code> navigation properties as <code>virtual</code> as well.</p>
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    1. POIs this normal Entity Framework behaviour
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    1. POIs this normal Entity Framework behaviour
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    1. COThat is an excellent explanation. I didn't know about Relationship Fixup. I have subsequently changed these properties to virtual to avoid logical, but not obvious behaviour of objects. Thank you very much for your help.
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